Kinematic Alignment and Novel Femoral and Tibial Prosthetics

ABSTRACT

A tibial component placement guide for use in a knee arthroplasty procedure involving a knee joint comprising a tibia, a patella, and a femur, the guide comprising an overlay configured to be overlaid a resected tibia, the overlay including at least one of an indicia and an opening indicative of at least one of an orientation and a position of at least one of a first axis of the femur, a second axis of the femur, and a first axis of the patella.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/979,034, entitled, “KINEMATIC ALIGNMENT OFFEMORAL AND TIBIAL COMPONENTS,” filed Apr. 14, 2014, and U.S.Provisional Patent Application Ser. No. 62/013,198, entitled, “KINEMATICALIGNMENT OF FEMORAL AND TIBIAL COMPONENTS,” filed Jun. 17, 2014, andU.S. Provisional Patent Application Ser. No. 62/022,894, entitled,“KINEMATIC ALIGNMENT OF FEMORAL AND TIBIAL COMPONENTS,” filed Jul. 10,2014, the disclosure of each of which is incorporated herein byreference.

INTRODUCTION TO THE INVENTION

The present disclosure is directed to knee kinematics as well astechniques, surgical guides, and orthopedic prosthetics to enhance kneearthroplasty.

Knee arthritis causes debilitating pain affecting activities of dailyliving. When pain is not well controlled by non-operative treatments andthe failure in managing disease′ symptoms (pain, stiffness, swelling,and/or bony spurs), Total Knee Arthroplasty (TKA) is recommended if thepatient is medically fit for the surgery and has no active infection.

One common objective in TKA is to restore normal kinematics. However,what are normal kinematics? Is it the relationship between ligamentsmenisci and articular surfaces of femur, tibia and patella or thedistribution of contact stresses across the articulating joint assymmetrically as possible, avoiding overloading of the one compartment?Although trying to achieve the same goal, these two philosophies requiredifferent surgical techniques—one to provide a restoration to normalanatomy (in the case of osteoarthritis), second is to correct defectiveanatomy (i.e. varus/valgus).

The former philosophy is a measured resection technique where bone andcartilage are replaced by implants that are of generally the samethickness. The latter philosophy is a balanced flexion gap techniquethat may require altering the patient's pre-arthritic anatomy. The majorassumption underlying this philosophy is many patients who developmedial compartment arthritis of the knee are bowlegged, or walk with avarus thrust, since childhood. Therefore, restoring the condition of thepre-arthritic alignment would result in greater varus component positionthan is generally considered acceptable for knee arthroplasty.

However, whether using measured resection or flexion gap surgicaltechnique, the predominant method of alignment is the mechanicallyaligned (mechanical neutral) TKA. In this method, the surgeon cuts thedistal femur and the proximal tibia perpendicular to the mechanical axes(Appendix A). The second alignment method, which is gaining moreacceptance, is the kinematically aligned TKA. The goal of this lattermethod is to restore the natural difference in symmetry and varus-valguslaxity between 0 degrees of extension and 90 degrees of the normal knee(Appendix B).

Prosthetic placement in TKA is a complex problem related to the complexshapes of the femur and tibia, out of plane geometrical relationships ofthe articular surfaces and bones, and the additive factor of ligamentouschanges, anatomical variation and deformity resulting from chronicdisease. The relationship between axial and rotational alignment is notwell documented. It is known that decreased femoral anteversion inCaucasians patients and decreased tibia torsion in Asian patients can beassociated with osteoarthritis. In one study, genu varum has beenassociated with external tibial torsion. It is likely that bothdeformations coexist in a typical three-dimensional deformity. Forexample, an externally rotated leg with the knee flexed will appear as avarus deformity. A logical conclusion is that detrimental jointoverloads can result from combined rotational and axial malalignment.

The instant disclosure involved analyzing both alignment methods andcoming to the conclusion that the current implant designs (femur, tibiaand instruments) are not well suited for the kinematic aligned TKA.

Surgical techniques in TKA have relied on recreating primarily the twodimensional mechanical axis alignment in the coronal plane (see FIGS.1A-1C and 2A), followed by carefully balancing the extension and flexiongaps (see FIG. 2B). Intrinsic to the latter process is coronal placementof the prosthetic implants in the sagittal plane. While distal measuredresection methods attempt to restore “normal” anatomy, by placingimplants in the “normal” position using mechanical alignment, this failsto account for underlying rotational deformities. For example, increasedknee version or external rotation of the transtibial axis compared tothe femoral transepicondylar axis may be an underlying deformity thatcontributes to varus misalignment.

In addition, the cuts that are made to the femur and tibia during TKAmay change the angle and the level of natural joint line causingabnormal tightening or slackening of the collateral, retinacular, andposterior cruciate ligaments and abnormal kinematics. The undesirableconsequences of the abnormal kinematics are instability, motion loss,accelerated component wear and component loosening from unevenload-sharing between compartments.

In order to better understand what the term natural kinematics meansseveral studies have been performed and published by various authors.One gold standard method requires analysis of digital fluoroscopicimages, taken during a series of activities. For each activity the poseof the femur relative to the tibia is tracked throughout—allowing forthe capture of the entire kinematic profile for each subject duringactivity (this process is well described in the document—and is easilyreferenced to existing literature if space saving is desired). Bothcontact maps, tracking the closest point between the two surfaces, andthe instantaneous axis of rotation (helical axis) suggest that the kneepivots clearly about the medial side, and rolls back on the lateralside. In fact, during deep knee bend, the medial side may experienceslight anterior translation—a motion sometimes referred to asparadoxical motion. Interestingly, this helical axis very closelyfollows the sagittal kinematic plane during all activity. This is shownin FIGS. 22-31.

Another clue as to how the normal knee behaves is uncovered withinvestigation of the ligament lengths during flexion. Looking at the MCLand LCL during flexion shows, as with the contact analysis, that the MCLlength changes very little during flexion compared to the LCL length—andhas significantly less translation than the LCL. This would suggest amedial side which is considerable tighter throughout flexion than thelateral. Further, the LCL is longest at full extension—suggesting arigid joint at extension and a fairly lax lateral side in extension, butstill fairly tight medially. Finally, when examining the PCL/ACL, weagain see significant length changes, but in a way that relates the PCLlength inversely to the ACL length, suggesting an “exchange” of loadduring flexion. It is worth mentioning that the posterior translation ofthe lateral side is not a linear one, but happens rapidly as the lateralcurvature of the femur transitions from the relatively flat surface inearly flexion and extension to the more curved posterior surface indeeper flexion. The soft tissue profiles of the normal knee duringactivity are totally counterintuitive to mechanical alignment andbalanced gaps. In fact, this helps to explain why mechanically alignedknees cannot achieve normal kinematics—the joint balance and joint lineshave been altered significantly. Thus a method is required which canalign the implant in a way to restore, or maintain, natural loading ofthe knee (not equal medial/lateral loads) and normal kinematics.

As part of the instant disclosure, X-ray fluoroscopy may be utilized togenerate two dimensional (2D) fluoroscopy images of components of ajoint across a range of motion of the joint. Thereafter, threedimensional models of the patient's anatomy, having already beenconstructed from static images (e.g., MRI, CT, X-ray, etc.) taken of thepatient anatomy, need to be registered to the 2D fluoroscopy images. Inthe instance circumstance, 2D fluoroscopy images are taken of a humanknee joint at distinct points along its range of motion, as well asconstruction of a 3D component model of the human knee joint. Inexemplary form, perspective images of the 3D joint model (comprising thefemur, tibia and the patella (with the fibula)) are overlaid onto the 2Dfluoroscopy images, across the range of motion, taking into account theposition of the X-ray source and to the image intensifier. When the 3Djoint model is correctly registered (i.e., overlaid) with the 2Dfluoroscopy images, the relative pose of the components of the 3D jointmodel is the same as the pose of those components at the time thefluoroscopy images were created. Registering the joint model to the 2Dfluoroscopy images across selected frames of the range of motion isutilized to calculate the relative pose between the three bones over theentire range of motion.

The pose of a rigid body {A} with respect to another coordinate system{B} can be represented by a six element vector ^(B) _(A)x=(^(B)x_(Aorg),^(B)y_(Aorg),^(B)z_(Aorg),α,β,γ)_(T), where^(B)p_(Aorg)=((^(B)x_(Aorg),^(B)y_(Aorg),^(B)z_(Aorg))^(T) is the originof frame {A} in frame {B}, and (□□□□□) are the angles of rotation of {A}about the (z, y, x) axes of {B}. An alternative representation oforientation is to use three elements of a quaternion; the conversionbetween Euler angles and quaternions is straightforward.

Equivalently, pose can be represented by a 4×4 homogeneoustransformation matrix:

${\,_{A}^{B}H} = \begin{pmatrix}{\,_{A}^{B}R} & {\,{{}_{}^{}{}_{}^{}}} \\0 & 1\end{pmatrix}$

where ^(B) _(A)R is the 3×3 rotation matrix corresponding to the angles(□□□□□). The letter H designates the equivalent 4×4 homogeneoustransformation matrix.

Homogeneous transformations are a convenient and elegant representation.Given a homogeneous point ^(A)p=(^(A)x_(p),^(A)y_(p),^(A)x_(p,1))^(T),represented in coordinate system {A}, it may be transformed tocoordinate system {B} with a simple matrix multiplication ^(B)p=_(A)^(B)H ^(A)p. The homogeneous matrix representing the pose of frame {B}with respect to frame {A} is just the inverse of the pose of {A} withrespect to {B}; i.e., _(B) ^(A) H=_(A) ^(B)H⁻¹. Finally, if one knowsthe pose of {A} with respect to {B}, and the pose of {B} with respect to{C}, then the pose of {A} with respect to {C} is easily given by thematrix multiplication _(A) ^(C)H=_(B) ^(C)H_(A) ^(B)H.

The pose of each bone in the joint model is represented by a 4×4homogeneous transformation matrix _(Tib) ^(Fem)H that is comprised ofrotation matrix and translation vector. The rotation matrix _(fluuro)^(Model)R_(xyz) (γ, β, α) is given by:

$\begin{matrix}\begin{matrix}{{{{}_{}^{}{}_{}^{}}( {\gamma,\beta,\alpha} )} = {{R_{z}(\alpha)}{R_{y}(\beta)}{R_{x}(\gamma)}}} \\{= {\begin{bmatrix}{{Cos}(\alpha)} & {- {{Sin}(\alpha)}} & 0 \\{{Sin}(\alpha)} & {{Cos}(\alpha)} & 0 \\0 & 0 & 1\end{bmatrix}*\begin{bmatrix}{{Cos}(\beta)} & 0 & {{Sin}(\beta)} \\0 & 1 & 0 \\{- {{Sin}(\beta)}} & 0 & {{Cos}(\beta)}\end{bmatrix}*}} \\{\begin{bmatrix}1 & 0 & 0 \\0 & {{Cos}(\gamma)} & {- {{Sin}(\gamma)}} \\0 & {{Sin}(\gamma)} & {{Cos}(\gamma)}\end{bmatrix}}\end{matrix} & \; \\{{{\,\mspace{20mu}}_{fluoro}^{Model}{R_{xyz}( {\gamma,\beta,\alpha} )}} = \begin{bmatrix}r_{11} & r_{12} & r_{13} \\r_{21} & r_{22} & r_{23} \\r_{31} & r_{32} & r_{33}\end{bmatrix}} & \;\end{matrix}$

whereby, β, and α are the model's angles of rotations about x, y, and zaxes, and the translation vector is^(Model)p_(fluoro)=(^(Model)x_(fluoro),^(Model)y_(fluoro),^(Model)z_(fluoro))^(T)respectively. Therefore, the relative pose) of the femur with respect tothe tibia is then calculated using the equation _(Tb) ^(Fem)H=_(Fluoro)^(Tib)H_(Fem) ^(Fluoro)H (similarly _(Fem) ^(Pat)H=_(Fluoro)^(Femb)H_(Pat) ^(Fluoro)H).

In accordance with the instant disclosure, three methods were utilizedfor analyzing the relative motion of the femur and tibia across a rangeof motion of a knee joint. The first method was the method of screw axisdecomposition, also called the helical axis of motion method. In thismethod, the axis in space about which the moving body rotates isdetermined. Simply put, the motion of a rigid body from one time instantto another can be decomposed as a rotation about an axis, plus atranslation along that axis. The axis is represented as a point on theaxis (C₀), along with a unit vector K specifying the direction of theaxis. The point C₀ and the vector K are represented in the coordinatesystem of the body at the first time instant. An initial computationuses the rotation matrix R to compute the rotation axis and angle:

θ=arccos((R ₁₁ +R ₂₂ +R ₃₃−1)/2)

K=[R ₃₂ −R ₂₃ R ₁₃ −R ₃₁ R ₂₁ −R ₁₂]^(T)/(2 sin(θ))

Thereafter, the components of translation parallel and perpendicular tothe rotation axis is computed:

T _(para)=(T·K)K

T _(perp) =T−T _(para)

Then, the vector C₀ is computed to the screw axis:

M=I _(3×3) −R

C ₀=(M ^(T) M)⁻¹ M ^(T) T _(perp)

where I_(3×3) is the 3×3 identity matrix. Note that the matrix M issingular.

The point C₀ is an arbitrary point on the axis, which may be far away.Sometimes it is useful to choose a specific point on the axis. In theinstant application, it is useful to find the point on the axis that isthe intersection of the axis with the XY plane of the body:

s=C _(0z) −K _(z)

P=C ₀ +sK

where C_(0z) and K_(z) are the z components of the vectors C₀ and K,respectively. Here, s is the distance from C0 to the XY plane, along thevector K. The point P is in the XY plane of the body at the firstposition.

The location and orientation of the helical axis of motion may bedefined with respect to the coordinate system of the tibia. If the kneewas a simple hinge joint, with pure rotation about the medial axis, thenthe helical axis of motion would be a stationary line perpendicular tothe sagittal plane. However, the motion of the knee joint is morecomplex than a simple hinge joint, and can include translation as wellas rotation about other axes. As a result, the helical axis of motion isnot exactly perpendicular to the sagittal plane, and is not fixed inspace. FIGS. 4A and 4B show how the helical axis of motion moves duringthe flexion sequence (from 0 degrees to 120 degrees of flexion) for anormal knee joint. FIGS. 4C and 4D show the geometrical center of thefemur rotating around the helical axis of motion.

A second method used to analyze the relative motion of the knee jointpursuant to the instant disclosure involved tracking the contact pathsof the femur on the tibia during a range of motion of the knee joint asevidenced by fluoroscopic images. The minimum point on the surface ofthe medial and lateral condyles for each respective flexion angle wascalculated automatically as the closest points to the tibia andprojected down onto the tibial plateau (see FIGS. 5A-5D). This methodmay be preferable because the process for obtaining these minimum pointsis automated and reproducible, thus reducing or eliminating humanerrors. It should be noted that these contact points are also located inthe coordinate space of the tibia.

As part of this second method, all anterior-posterior (AP) measurementswere made with respect to a plane (frontal) that is located at thegeometric center of the tibia (see FIG. 6), while the geometric centerwas calculated automatically. If the AP contact position of the condyleis more anterior than this plane, the AP position will be positive. Incontrast, if the contact position is more posterior than this plane, theAP position will be negative. For each selected frame of the fluoroscopyimage sequence of a patient's knee joint, femorotibial contact pathswere determined for the medial and lateral condyles and plotted withrespect to knee flexion angle (see FIGS. 7-9).

As part of this second method, fluoroscopic images of a patients' kneejoints with normal structure and kinematics were obtained that includedin the range of motion a deep knee bend. Patient's performing this deepknee bend experienced posterior femoral translation of their lateralcondyle and minimal change in the position of the medial condyle (seeFIG. 7). The average amount of posterior femoral translation of thelateral condyle was 28.68 mm (standard deviation, 5.45), whereas theaverage medial condyle translation was 1.5 mm (standard deviation,2.19), in the posterior direction. The majority of the posterior femoraltranslation of the lateral condyle appeared to occur in the first 75°knee flexion (see FIG. 8). Posterior femoral translation was not alwayscontinuous with increasing knee flexion because small amounts ofparadoxical anterior translation of femorotibial contact were observedin midflexion, particularly medially.

As evidenced from the fluoroscopic images of patients with normal kneestructure and kinematics, patients' knees experienced a normal axialrotation pattern during a deep knee bend (tibia internally rotating withincreased knee flexion), because the posterior translation offemorotibial contact laterally was greater than that observed medially(see FIG. 7). The average amount of axial rotation for the normalsubjects from 0° to 120° flexion was 18.39° (standard deviation, 6.09)in the normal direction. The majority of this rotation occurred in thefirst 30° knee flexion (average, 9.35°, see FIG. 9). Anteroposteriorcontact points for patients with normal knees are represented in FIGS.10A-10E. Rotational movements are best represented by describing thehelical axis of motion across a range of motion.

The helical axis of motion is an imaginary line in space, around whichthe femur rotates. Because of the out of plane motion of the knee (6degrees of freedom), this axis is almost never perpendicular to thesagittal plane (see FIGS. 11A-11D). By closely looking at the femoralrotations in represented in FIGS. 11A-11D, it was observed that thehelical axis translates posteriorly. Therefore, posterior femoraltranslation is a combination of pure AP linear motion and rotation ofthe femur relative to the tibia.

A third method utilized to analyze the relative motion of the knee jointpursuant to the instant disclosure included tracking the paths ofspecific contact areas on the distal and posterior anatomy of the femuron the tibia (see FIGS. 16A, 16B, 17A, 17B). Like the second method,this third method measured the overall posterior femoral rollback fromfluoroscopic images of normal knee joints taken through a range ofmotion by projecting the lowest point of the femoral condyles on thetibial condyles and then determined the motion of the femur with respectto the tibia by tracking the path of the femoral condyles on the tibialcondyles. However in this method the morphology of the femoral condylesand tibial plateaus were never studied properly with kinematics. Theposterior femoral rollback is a more complicated process which softtissues play a significant part.

Using the 3D-to-2D registration method described previously with respectto the first method, the 3D patient bone models were overlaid onto thefluoroscopic images. Relative rotations of the femur to the tibia werecalculated at every 20 degrees of flexion using the 3D motion captured.In addition, at least one of computed tomography (CT) scans and magneticresonance imaging (MRI) scans were obtained for each knee joint havingbeen the subject of the fluoroscopic images. From the CT and/or MIRscans, the origin and insertion points were marked on the femur, fibula,and tibia models for the Anterior Cruciate Ligament (ACL), PosteriorCruciate Ligament (PCL), Medial Collateral Ligament (MCL) and LateralCollateral Ligament (LCL). Using the rotational matrices methodspreviously described in paragraphs [0013]-[0018], the origin andinsertion points were calculated and tracked during the motion (see FIG.12). Finally, a 3D dimensional surface model of the ACL and PCL was fitto the origin and insertion points on the femur, tibia, and fibula (seeFIG. 13) for each discrete point along the range of motion correspondingto the fluoroscopic images. Thereafter, an algorithm was utilized tocalculate the ligament lengths across the entire range of motion (seeFIGS. 14 and 15).

As evidenced in FIGS. 14 and 15, the ACL ligament had a calculated amaximum length of 37.7±4.8 mm at maximum extension of the knee while thePCL ligament had a calculated maximum length of 44.586±3.7 mm at maximumflexion of the knee. In summary, the ACL and PCL tend to act in oppositedirections because as one ligament elongates the other ligamentretracts.

After including the soft tissues (ACL/PCL, MCL/LCL) and morphology ofthe knee, it was observed that the motion of lateral femoral condyledoes not just continuously rollback. In order to understand this motion,the four contact areas A1, A2, A3 and A4 depicted in FIGS. 16A-17B wereexamined. From this examination, a number of questions were raised.First, among these questions, was how could lateral condyle motion becontinuous when the lateral condyle has almost no curvature. The lateralfemoral condyle is longer in length than the lateral tibial condyle andyet the lateral femoral condyle stays in contact on the tibial plateau.Essentially, it was observed that the motion of lateral condyle behaveslike a cam.

Referring to FIGS. 16A-17B, by examining the morphology of the medialand lateral tibial condyles, it is clear that after 40 degrees offlexion the PCL gets engaged (pulling) and forces some rotational motionthat results in anterior femoral medial condyle movement while slightlyrotating at 40 degrees (see FIG. 16, area A1). After 40 degrees offlexion, specifically around 60 degrees, the lateral femoral condylecontact area A4 experiences maximum posterior femoral rollback.Similarly, the medial condyle contact area A3 experiences maximumposterior motion. After 60 degrees, the motion of lateral femoralcondyle continues until the posterior lateral femoral condyle curvaturematches the proper lateral tibial curvature. In summary the medial andlateral condyle contact areas (A1/A2 and A3/A4) motion is divided in twodistinct patterns of movement governed by the cam motion of the lateralcondyle.

No currently available TKA consistently reproduces the kinematic patternobserved in the normal knee. Along with the inability to provide nativekinematics, most patients having TKA fail to achieve full function whencompared with a sex and age matched group. More importantly, weightbearing knee flexion is significantly reduced compared with passiveflexion and only a small subset of patients undergoing TKA obtain morethan 120 degrees flexion in weight bearing deep knee bend. Part of thereasons of the failure of the current implants to reproduce normalkinematic patterns is the absence of evaluating: (1) the relationshipsbetween underlying joint deformity and preoperative alignment in vivojoint kinematics, and (2) the relationships between rotational deformityand the subsequent effect on the in vivo joint. Furthermore, there is anabsence of evaluating the effect of standard surgical techniques (e.g.,gap balance) on joint kinematics. Thus, there is a need in the art forsurgical solutions as part of TKA to consistently approach thekinematics of a natural knee.

It is a first aspect of the present invention to provide a tibialcomponent placement guide for use in a knee arthroplasty procedureinvolving a knee joint comprising a tibia, a patella, and a femur, theguide comprising an overlay configured to be overlaid a resected tibia,the overlay including at least one of an indicia and an openingindicative of at least one of an orientation and a position of at leastone of a first axis of the femur, a second axis of the femur, and afirst axis of the patella.

In a more detailed embodiment of the first aspect, the overlay includesan opening indicative of the orientation of the first axis of the femurand the second axis of the femur. In yet another more detailedembodiment, the opening comprises a through hole. In a further detailedembodiment, the through hole outlines a T-shape, a horizontal aspect ofthe T-shape is indicative of orientation of the first axis of the femur,and a vertical aspect of the T-shape is indicative of orientation of thesecond axis of the femur. In still a further detailed embodiment, thethrough hole outlines a + shape, a horizontal aspect of the + shape isindicative of orientation of the first axis of the femur, and a verticalaspect of the + shape is indicative of orientation of the second axis ofthe femur. In a more detailed embodiment, the opening comprises a firstthrough hole and a second through hole, the first through hole isindicative of the first axis of the femur, and the second through holeis indicative of orientation of the second axis of the femur. In a moredetailed embodiment, the opening comprises a first cutout and a secondcutout, the first cutout is indicative of the first axis of the femur,and the second cutout is indicative of orientation of the second axis ofthe femur. In another more detailed embodiment, the first axis of thefemur comprises the posterior condylar axis of the femur. In yet anothermore detailed embodiment, the second axis of the femur comprises thehelical axis of the femur. In still another more detailed embodiment,the overlay has a contour outline that is aligned with the resectedtibia.

In yet another more detailed embodiment of the first aspect, the contouroutline is patient-specific. In yet another more detailed embodiment,the tibial component placement guide further includes at least one of anindicia and an opening indicative of at least two of a medial guide, alateral guide, a size of the guide, and a particular patient. In afurther detailed embodiment, the guide is fabricated from at least oneof titanium, a titanium alloy, stainless steel, and a stainless steelalloy. In still a further detailed embodiment, the guide includes athrough aperture configured to align a through fastener mounted to theresected tibia. In a more detailed embodiment, the through fastenercomprises a pin. In a more detailed embodiment, the through aperturecomprises a plurality of through apertures, and each of the plurality ofapertures is configured to receive a pin. In another more detailedembodiment, the overlay comprises a base plate. In yet another moredetailed embodiment, he base plate includes a flange along a peripheryof the base plate. In still another more detailed embodiment, the tibialcomponent placement guide further includes at least one of an indiciaand an opening indicative of the orientation of a third axis of thefemur, the third axis being parallel to the first axis.

It is a second aspect of the present invention to provide a method ofusing a tibial component placement guide for use in a knee arthroplastyprocedure involving a knee joint comprising a tibia, a patella, and afemur, the method comprising: (a) applying an overlay to a resectedtibia, the overlay including at least one of an indicia and an openingindicative of at least one of an orientation and a position of at leastone of a first axis of the femur, a second axis of the femur, and afirst axis of the patella; (b) marking the resected tibia with at leastone mark using the overlay to denote at least one of an orientation anda position of at least one of a first axis of the femur, a second axisof the femur, and a first axis of the patella; and, (c) orienting andattaching at least one of an orthopedic tibial tray trial and anorthopedic tibial tray to the resected tibia using the mark.

In a more detailed embodiment of the second aspect, the step of applyingthe overlay includes aligning a peripheral shape of the overlay with aperipheral shape of the resected tibia and placing the overlay on top ofthe resected tibia. In yet another more detailed embodiment, the overlayincludes an opening indicative of the orientation of the first axis ofthe femur and the second axis of the femur. In a further detailedembodiment, the opening comprises a through hole. In still a furtherdetailed embodiment, the through hole outlines a T-shape, a horizontalaspect of the T-shape is indicative of orientation of the first axis ofthe femur, and a vertical aspect of the T-shape is indicative oforientation of the second axis of the femur. In a more detailedembodiment, the through hole outlines a + shape, a horizontal aspect ofthe + shape is indicative of orientation of the first axis of the femur,and a vertical aspect of the + shape is indicative of orientation of thesecond axis of the femur. In a more detailed embodiment, the openingcomprises a first through hole and a second through hole, the firstthrough hole is indicative of the first axis of the femur, and thesecond through hole is indicative of orientation of the second axis ofthe femur. In another more detailed embodiment, the opening comprises afirst cutout and a second cutout, the first cutout is indicative of thefirst axis of the femur, and the second cutout is indicative oforientation of the second axis of the femur. In yet another moredetailed embodiment, the first axis of the femur comprises the posteriorcondylar axis of the femur. In still another more detailed embodiment,the second axis of the femur comprises the helical axis of the femur.

In yet another more detailed embodiment of the second aspect, theoverlay has a contour outline that is aligned with the resected tibia.In yet another more detailed embodiment, the contour outline ispatient-specific. In a further detailed embodiment, the overlay furtherincludes at least one of an indicia and an opening indicative of atleast two of a medial guide, a lateral guide, a size of the guide, and aparticular patient. In still a further detailed embodiment, the guide isfabricated from at least one of titanium, a titanium alloy, stainlesssteel, and a stainless steel alloy. In a more detailed embodiment, theguide includes a through aperture configured to align a through fastenermounted to the resected tibia. In a more detailed embodiment, thethrough fastener comprises a pin. In another more detailed embodiment,the through aperture comprises a plurality of through apertures, andeach of the plurality of apertures is configured to receive a pin. Inyet another more detailed embodiment, the overlay comprises a baseplate. In still another more detailed embodiment, the base plateincludes a flange along a periphery of the base plate.

In a more detailed embodiment of the second aspect, the overlay furthercomprises at least one of an indicia and an opening indicative of theorientation of a third axis of the femur, the third axis being parallelto the first axis. In yet another more detailed embodiment, the at leastone mark comprises a pin, and the step of marking the resected tibiaincludes fastening the at least one pin to the resected tibia. In afurther detailed embodiment, the at least one mark comprises anindentation formed into the resected tibia, and the step of marking theresected tibia includes using a punch to form the indentation into theresected tibia. In still a further detailed embodiment, the at least onemark comprises a representation formed into the resected tibia, and thestep of marking the resected tibia includes writing the representationonto the resected tibia. In a more detailed embodiment, the orientingand attaching step includes orienting and attaching an orthopedic tibialtray to the resected tibia using the mark. In a more detailedembodiment, the method further includes removing the overlay prior toorienting and attaching at least one of the orthopedic tibial tray trialand the orthopedic tibial tray to the resected tibia using the mark. Inanother more detailed embodiment, the overlay includes an openingindicative of the orientation of the first axis of the patella. In yetanother more detailed embodiment, the opening comprises a through hole.

It is a third aspect of the present invention to provide a method offabricating a tibial component placement guide for use in a kneearthroplasty procedure involving a knee joint comprising a tibia, apatella, and a femur, the method comprising generating a tibialcomponent placement guide that typifies at least one of a shape and anoutline of a resected tibia, along with at least one identifierrepresentative of at least one of a position and an orientation of akinematic axis of at least one of the femur and the patella.

In a more detailed embodiment of the third aspect, the tibial componentguide typifies at least one of the shape of the resected tibia, and thetibial component guide is mass-customized. In yet another more detailedembodiment, the tibial component guide typifies at least one of theoutline of the resected tibia, and the tibial component guide ismass-customized. In a further detailed embodiment, the tibial componentguide typifies at least one of the shape of the resected tibia, and thetibial component guide is patient-specific. In still a further detailedembodiment, the tibial component guide typifies at least one of theoutline of the resected tibia, and the tibial component guide ispatient-specific. In a more detailed embodiment, the at least oneidentifier is representative of an orientation of the kinematic axis ofthe femur, and the kinematic axis comprises a femoral post condylaraxis. In a more detailed embodiment, the at least one identifier isoriented parallel to the femoral post condylar axis. In another moredetailed embodiment, the at least one identifier is representative of aposition of the kinematic axis of the femur, and the kinematic axiscomprises a femoral helical axis. In yet another more detailedembodiment, the position of the at least one identifier isrepresentative of a projected position of the femoral helical axis ontothe resected tibia. In still another more detailed embodiment, the atleast one identifier is representative of the position of the kinematicaxis of the patella, and the kinematic axis comprises a patellatransverse axis.

In yet another more detailed embodiment of the third aspect, the atleast one identifier is representative of the orientation of thekinematic axis of the patella, and the kinematic axis comprises apatella transverse axis. In yet another more detailed embodiment, the atleast one identifier is representative of a position of the kinematicaxis of the femur, and the kinematic axis of the femur is parallel tothe sagittal kinematic plane of the femur. In a further detailedembodiment, the position of the at least one identifier isrepresentative of a projected position of the sagittal kinematic planeonto the resected tibia. In still a further detailed embodiment, themethod further includes establishing at least one of the shape and theoutline of the resected tibia. In a more detailed embodiment, the stepof establishing at least one of the shape and the outline of theresected tibia includes performing a virtual resection upon a tibialbone model to generate a virtual resected tibia. In a more detailedembodiment, the virtual resected tibia is analyzed to generate a twodimensional shape of a virtual resected surface, and the two dimensionalshape of the virtual resected surface typifies the shape of the resectedtibia. In another more detailed embodiment, the virtual resected tibiais analyzed to generate a two dimensional outline of a virtual resectedsurface, and the two dimensional outline of the virtual resected surfacetypifies the outline of the resected tibia. In yet another more detailedembodiment, the method further includes establishing at least one of theposition and the orientation of the kinematic axis of at least one ofthe femur and the patella when superimposed onto the tibia. In stillanother more detailed embodiment, the kinematic axis comprises at leastone of a femoral helical axis, a femoral post condylar axis, a patellatransverse axis, a femoral sagittal kinematic plane, and a patellasagittal kinematic plane.

In a more detailed embodiment of the third aspect, the step ofestablishing at least one of the position and the orientation of thekinematic axis when superimposed onto the tibia includes at least one ofestablishing a femoral helical axis with respect to the femur,establishing a femoral post condylar axis with respect to the femur,establishing a patella transverse axis with respect to the patella,establishing a femoral sagittal kinematic plane with respect to thefemur, and establishing a patella sagittal kinematic plane with respectto the patella. In yet another more detailed embodiment, the step ofestablishing at least one of the position and the orientation of thekinematic axis when superimposed onto the tibia includes establishingthe femoral helical axis with respect to the femur, and the step ofestablishing the femoral helical axis with respect to the femurcomprises analyzing the relative motion of the femur with respect to thetibia. In a further detailed embodiment, the step of analyzing therelative motion of the femur with respect to the tibia includesanalyzing tracked contact points between the tibia and the femur usingfluoroscopy. In still a further detailed embodiment, the step ofanalyzing the relative motion of the femur with respect to the tibiaincludes analyzing tracked contact paths of the femur with respect tothe tibia using fluoroscopy. In a more detailed embodiment, the step ofestablishing at least one of the position and the orientation of thekinematic axis when superimposed onto the tibia includes establishingthe femoral post condylar axis with respect to the femur, and the stepof establishing the femoral post condylar axis with respect to the femurcomprises analyzing the relative motion of the femur with respect to thetibia. In a more detailed embodiment, the step of analyzing the relativemotion of the femur with respect to the tibia includes analyzing trackedcontact points between the tibia and the femur using fluoroscopy. Inanother more detailed embodiment, the step of analyzing the relativemotion of the femur with respect to the tibia includes analyzing trackedcontact paths of the femur with respect to the tibia using fluoroscopy.

In a more detailed embodiment of the third aspect, the step ofestablishing at least one of the position and the orientation of thekinematic axis when superimposed onto the tibia includes establishingthe femoral sagittal kinematic plane with respect to the femur, and thestep of establishing the femoral sagittal kinematic plane with respectto the femur comprises analyzing the relative motion of the femur withrespect to the tibia. In yet another more detailed embodiment, the stepof analyzing the relative motion of the femur with respect to the tibiaincludes analyzing tracked contact points between the tibia and thefemur using fluoroscopy. In a further detailed embodiment, the step ofanalyzing the relative motion of the femur with respect to the tibiaincludes analyzing tracked contact paths of the femur with respect tothe tibia using fluoroscopy. In still a further detailed embodiment, thestep of establishing at least one of the position and the orientation ofthe kinematic axis when superimposed onto the tibia includesestablishing the patella transverse axis with respect to the patella,and the step of establishing the patella transverse axis with respect tothe patella comprises analyzing the relative motion of the patella withrespect to the femur. In a more detailed embodiment, the step ofanalyzing the relative motion of the patella with respect to the femurincludes analyzing tracked contact points between the patella and thefemur using fluoroscopy. In a more detailed embodiment, the step ofanalyzing the relative motion of the patella with respect to the femurincludes analyzing tracked contact paths of the patella with respect tothe femur using fluoroscopy. In another more detailed embodiment, thestep of establishing at least one of the position and the orientation ofthe kinematic axis when superimposed onto the tibia includesestablishing the patella sagittal kinematic plane with respect to thepatella, and the step of establishing the patella sagittal kinematicplane with respect to the patella comprises analyzing the relativemotion of the patella with respect to the femur.

In yet another more detailed embodiment of the third aspect, the step ofanalyzing the relative motion of the patella with respect to the femurincludes analyzing tracked contact points between the patella and thefemur using fluoroscopy. In yet another more detailed embodiment, thestep of analyzing the relative motion of the patella with respect to thefemur includes analyzing tracked contact paths of the patella withrespect to the femur using fluoroscopy. In a further detailedembodiment, the tibial component placement guide includes an openingindicative of the orientation of the first axis of the femur and thesecond axis of the femur. In still a further detailed embodiment, theopening comprises a through hole. In a more detailed embodiment, thethrough hole outlines a T-shape, a horizontal aspect of the T-shape isindicative of orientation of the first axis of the femur, and a verticalaspect of the T-shape is indicative of orientation of the second axis ofthe femur. In a more detailed embodiment, the through hole outlines a +shape, a horizontal aspect of the + shape is indicative of orientationof the first axis of the femur, and a vertical aspect of the + shape isindicative of orientation of the second axis of the femur. In anothermore detailed embodiment, the opening comprises a first through hole anda second through hole, the first through hole is indicative of the firstaxis of the femur, and the second through hole is indicative oforientation of the second axis of the femur. In yet another moredetailed embodiment, the opening comprises a first cutout and a secondcutout, the first cutout is indicative of the first axis of the femur,and the second cutout is indicative of orientation of the second axis ofthe femur. In still another more detailed embodiment, the first axis ofthe femur comprises the posterior condylar axis of the femur.

In a more detailed embodiment of the third aspect, the second axis ofthe femur comprises the helical axis of the femur. In yet another moredetailed embodiment, the tibial component placement guide has a contouroutline that is aligned with the resected tibia. In a further detailedembodiment, the contour outline is patient-specific. In still a furtherdetailed embodiment, the guide further includes at least one of anindicia and an opening indicative of at least two of a medial guide, alateral guide, a size of the guide, and a particular patient. In a moredetailed embodiment, the guide is fabricated from at least one oftitanium, a titanium alloy, stainless steel, and a stainless steelalloy. In a more detailed embodiment, the guide includes a throughaperture configured to align a through fastener mounted to the resectedtibia. In another more detailed embodiment, the through fastenercomprises a pin.

In a more detailed embodiment of the third aspect, the through aperturecomprises a plurality of through apertures, and each of the plurality ofapertures is configured to receive a pin. In yet another more detailedembodiment, the tibial component placement guide comprises a base plate.In a further detailed embodiment, the base plate includes a flange alonga periphery of the base plate. In still a further detailed embodiment,the tibial component placement guide further comprises at least one ofan indicia and an opening indicative of the orientation of a third axisof the femur, the third axis being parallel to the first axis. In a moredetailed embodiment, the at least one mark comprises a pin, and the stepof marking the resected tibia includes fastening the at least one pin tothe resected tibia. In a more detailed embodiment, the at least one markcomprises an indentation formed into the resected tibia, and the step ofmarking the resected tibia includes using a punch to form theindentation into the resected tibia.

In a more detailed embodiment of the third aspect, the at least one markcomprises a representation formed into the resected tibia, and the stepof marking the resected tibia includes writing the representation ontothe resected tibia. In yet another more detailed embodiment, theorienting and attaching step includes orienting and attaching anorthopedic tibial tray to the resected tibia using the mark. In afurther detailed embodiment, the method further includes removing thetibial component placement guide prior to orienting and attaching atleast one of the orthopedic tibial tray trial and the orthopedic tibialtray to the resected tibia using the mark.

It is a fourth aspect of the present invention to provide a kinematicfemoral component for use in a knee arthroplasty procedure involving aknee joint comprising a tibia, a patella, and a femur, the kinematicfemoral component comprising a femoral component replicating a naturaltrochlear groove angle of a femur that is parallel to a sagittal femoralkinematic plane.

In a more detailed embodiment of the fourth aspect, a lateral aspect ofan anterior flange extends proximally, the respect to a femur, between10 to 45 millimeters beyond a femoral knee center of the femur. In yetanother more detailed embodiment, a lateral aspect of an anterior flangeextends proximally, the respect to a femur, between 10 to 25 millimetersbeyond a femoral knee center of the femur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are anatomical frontal, anatomical profile, and skeletalsection views depicting the femoral and tibial mechanical axis.

FIG. 2A is a software user interface of an exemplary software system inaccordance with the instant disclosure showing hip, knee, and ankle(HKA) axes.

FIG. 2B is a graphical depiction of a gap balance technique used duringa knee arthroplasty procedure.

FIGS. 3A and 3B are X-ray fluoroscopic images of a knee joint bentapproximately 90 degrees, as well as a compilation image showing theposition of the femoral head and femoral condyles across a range ofmotion.

FIGS. 4A-4D are helical axes of motion corresponding to nine steps ofknee flexion from 0 to 120 degrees, shown in an sagittal plane, ananteroposterior view of axes projected on the frontal plane. Thegeometrical center of the femur rotating around the screw/helical axisshown in a sagittal and an anteroposterior view of the geometricalcenters of the femur projected on the frontal plane.

FIGS. 5A-5D include a frontal view of the knee joint showing the minimumpoints on the femoral condyles projected on the tibial plateau. Asagittal view of the knee joint showing 3 flexion angles and theircorresponding lowest points projected on the tibial plateau. Ananteroposterior view of the knee joint showing the three lowest pointson the femur projected on the frontal plane. An axial view of theminimum points projected on the tibial plateau. Finally, a top view ofthe tibial plateau showing a plane going through the geometrical centerof the tibia of knee joint.

FIG. 6 is a top view of the tibial plateau showing a plane going throughthe geometrical center of the tibia of knee joint.

FIG. 7 is a graphical representation of the top of a tibia and theaverage normal subjects' medial and lateral condyle contact positionsduring a deep knee bend activity.

FIG. 8 is a plot of anteroposterior translations of the contact pointsbetween the femur and the tibia during knee flexion.

FIG. 9 is a plot of axial rotation of the femur during knee flexion fornormal subjects.

FIGS. 10A-10E are axial, top views of the minimum points projected onthe tibial plateau of five subject knees showing clear medial pivotingmotion of the femur relative to the tibia.

FIGS. 11A-11D depict helical axis of the normal knees showing the axisdoes not stay fixed in space during an entire movement through theavailable range of motion across four subject knees.

FIG. 12 is a graphical depiction of ligament attachment sites trackedduring fluoroscopy of a knee joint.

FIG. 13 is a series of views of a virtual knee joint model showingligaments reconstructed using ligament attachment sites.

FIG. 14 is a plot depicting average lengths in millimeters for theanterior cruciate ligament and the posterior collateral ligament at eachincrement of flexion during a deep knee bend.

FIG. 15 is a table detailing subjects lengths in millimeters for theanterior cruciate ligament and the posterior collateral ligament at eachincrement of flexion during deep knee bend.

FIGS. 16A and 16B are distal and posterior views of a posterior end of afemur.

FIGS. 17A and 17B are projections of tracked areas from the femur ontothe tibia from zero degrees to 140 degrees projected on the tibia leftA1/A2 and right A3/A4 from FIGS. 16A, 16B.

FIGS. 18A-18D include medial, lateral, and posterior views of a femur,along with associated curves depicting the curvature differences alongthe length of the medial and lateral condyles.

FIG. 19 is an elevated perspective view of a virtual femur model showinga series of surface points placed on the lateral and medial condyles onthe posterior aspect.

FIG. 20 is an end view of a virtual femur model having a sphere fit toeach of the medial and lateral condyles using the surface points in FIG.19 in accordance with the present disclosure.

FIG. 21 is an end view of a virtual femur model having a cylinder fit toeach of the medial and lateral condyles using the surface points in FIG.19 in accordance with the present disclosure.

FIG. 22 is a graphical representation of a distal femur and comparisonof the surgical transepicondylar axis, the clinical transepicondylaraxis, the spherical axis, and the cylindrical axis.

FIG. 23 is a range of motion view showing how the femur moves withrespect to the tibia and how the position of the femoral helical axischanges with this motion.

FIG. 24 is a graphical depiction showing how the femoral cylindricalaxis changes across a range of motion between full extension (zerodegrees) and a deep knee bend (152 degrees).

FIG. 25 is a graphical depiction showing how the femoral spherical axischanges across a range of motion between full extension (zero degrees)and a deep knee bend (152 degrees).

FIG. 26 is a graphical depiction showing how the femoraltransepicondylar axis changes across a range of motion between fullextension (zero degrees) and a deep knee bend (152 degrees).

FIG. 27 is a graphical depiction of the clinical and surgicaltransepicondylar axis of the femur.

FIG. 28 is an overlay compilation of the graphical depictions from FIGS.24-26.

FIGS. 29A and 29B includes a range of motion view of the femur withrespect to the tibia and an overhead view of the tibia showing how thehelical/transverse axis of the femur changes with this range of motion.

FIG. 30 is a graphical representation showing the cylindrical axis ofthe femur is not normal with respect to the tibial mechanical axis.

FIG. 31 is a graphical representation of the distal femur showing theposterior condylar axis and the cylindrical axis are almost consistentlyparallel.

FIGS. 32A-32D are multiple views of a femur showing patella motion andtracking this motion in accordance with the instant disclosure via theintersection with the sagittal kinematic plane.

FIGS. 33A-33F are a series of images depicting how the motion of thepatella is tracked with respect to the sagittal kinematic plane.

FIG. 34 is a graphical depiction of a patella virtual model constructedfrom surface points across four quadrants.

FIGS. 35A and 35B are medial and lateral views of a femur showing thenatural motion of the patella contact surfaces with respect to thefemoral trochlear groove.

FIGS. 36A-36D are various views showing how the contact surfaces of thepatella embodies roughly the same curvature as the trochlear groove.

FIG. 37 depicts graphically the angular differences between the sagittalkinematic plane, the patella loci plane, and the femoral implant plane.

FIGS. 38A-38C are graphical depictions of motion of the patella beforeand after TKA and showing that post TKA the patella no longer replicatesits natural kinematic motion.

FIG. 39 is an end view of a TKA femoral component constructed inaccordance with the instant disclosure that includes a trochlear groovethat is kinematically aligned.

FIG. 40 is an end view of a distal femur showing how present dayimplants trochlear groove is considerably different from the trochleargroove of the kinematic femoral component fabricated in accordance withthe instant disclosure.

FIGS. 41A-41C depict initially the femoral postcondylar axis (PCA) andthe intersection of a plane normal to the PCA, and then depict theintersection of a plane normal to the PCA with a plane normal to thetibial mechanical axis, and finally depicting the a plane normal to thePCA imposed onto the proximal tibia.

FIG. 42 is a graphical representation of the proximal tibia havingcalculated traditional tibia landmarks that include the medial eminence,lateral eminence, and AP1/3 Tubercle posterior cruciate ligament.

FIGS. 43A and 43B are graphical representations showing how the Cobbaxis is determined using peripheral points on the medial and lateralcondyles and circles approximating the curvature of the condyles.

FIGS. 44A-44C comprises multiple views of positions of the femur withrespect to the tibia across a range of motion that are either loadbearing (red) or non-load bearing (blue).

FIG. 45 is an overhead view of a proximal tibia showing the orientationof various axes.

FIG. 46 is a comparison overhead view showing mechanical alignmentversus kinematic alignment of a commercially available tibial tray on aproximal tibia.

FIG. 47 is an overhead view showing mechanical alignment of acommercially available tibial tray on a proximal tibia.

FIG. 48 is an overhead view showing kinematic alignment of acommercially available tibial tray on a proximal tibia.

FIG. 49 is an overhead view showing kinematic alignment of a smallercommercially available tibial tray on a proximal tibia.

FIGS. 50A and 50B are comparison views showing femoral componentalignment when aligned with the femoral PCA.

FIGS. 51A and 51B are comparison views showing femoral componentalignment when aligned with the femoral PCA plus three degrees ofoffset.

FIG. 52 shows femoral component rotational alignment.

FIGS. 53A and 53B show multiple views of kinematic alignment betweenfemoral and tibial components of a TKA.

FIGS. 54A and 54B show multiple views of a femoral component withrespect to a tibial component using mechanical alignment and kinematicalignment (PPNP).

FIG. 55 is a process flow diagram depicting an exemplary process forgenerating an optimal implant placement.

FIGS. 56A and 56B are graphical depictions of initial tibial placementpursuant to the process flow diagram of FIG. 55.

FIGS. 57A and 57B are outline comparisons of the resected tibia and acommercially available tibial tray implant.

FIGS. 58A and 58B are graphical depictions showing the difference intibial tray placement on a resected tibia in accordance with the processof FIG. 55, where the initial alignment is refined to the weightedmatch.

FIG. 59 comprises a series of commercially available tibial trayimplants grouped according to alignment technique.

FIG. 60 is an overhead view of a tibia superimposed with the images offour commercially available tibial trays positioned via mechanicalalignment.

FIG. 61 is an overhead view of a tibia superimposed with the images offour commercially available tibial trays positioned via kinematicalignment in accordance with the instant disclosure.

FIG. 62 is an overhead view of a tibia superimposed with the images offour commercially available tibial trays positioned via refinedmechanical alignment.

FIG. 63 includes a series of overhead views of a tibia having mountedthereto the first and fourth commercially available tibial tray inaccordance with mechanical alignment (AAP), in accordance with kinematicalignment (PPNP), and in accordance with a refined mechanical alignment(TechMah).

FIG. 64 includes a series of overhead views of a tibia having mountedthereto the second and third commercially available tibial tray inaccordance with mechanical alignment (AAP), in accordance with kinematicalignment (PPNP), and in accordance with a refined mechanical alignment(TechMah).

FIG. 65 is an exemplary process diagram for calculating a posteriortibial axis using a statistical atlas.

FIG. 66 is an elevated perspective view of a tibia and femur, along withan MRI image, confirming that the PCA for femur and tibia seldom liealong an image plane.

FIGS. 67A-67E includes overhead views of a tibia and of a femur on atibia and how the PCA vary between the tibia and femur during rotation,along with a data set correlating the femoral PCA and Cobb axis.

FIGS. 68A-68C include graphical depictions of clusters and groupingsthat result from clustering data, as well as how the AP and MLdimensions are calculated/measured.

FIGS. 69A-69C include graphical depictions resection plane heightvariances and an average resection plane outline for a resected tibia.

FIGS. 70A-70C include graphical depictions resection plane varus andvalgus variances and an average resection plane outline for a resectedtibia.

FIGS. 71A-71C include graphical depictions resection plane posteriorslope variances and an average resection plane outline for a resectedtibia.

FIGS. 72A 72C 72B include graphical depictions showing how an asymmetrictibial tray covers the resected tibia well, but is rotated incorrectlywith respect to the projected femoral PCA.

FIGS. 73A and 73B are multiple views of a first exemplary tibial traytrial fabricated in accordance with the instant disclosure.

FIGS. 74A and 74B are multiple views of a second exemplary tibial traytrial fabricated in accordance with the instant disclosure.

FIG. 75 is a graphical depiction of a process flow for patient specifickinematic guide fabrication.

FIG. 76 is an image of a resected tibia showing consistency betweenmeasured and calculated kinematic axes.

FIG. 77 is an overhead view of a mass customized kinematic alignmentguide for a resected tibia fabricated in accordance with the instantdisclosure.

FIGS. 78A and 78B are multiple views of the mass customized kinematicalignment guide of FIG. 77 that account for retention of the posteriorcruciate ligament during TKA.

FIGS. 79A and 79B are multiple views, one showing the outline of aresected tibia and using the statistical atlas to determine the locationof the posterior cruciate ligament, as well as a second showing apossible design for a kinematic friendly tibial tray that does notimpinge upon the posterior cruciate ligament.

FIG. 80 is a graph showing high variability of setting tibial rotationusing present day method (non-kinematic methods).

FIG. 81 is a graph showing placement error of kinematic placements usinga guide in accordance with the instant disclosure, as validated througha software study.

FIG. 82 is a screen capture during the software validation studygraphically depicted in FIG. 81.

FIG. 83 is a picture of a plurality of mass-customized tibial componentkinematic placement guides fabricated in accordance with the instantdisclosure, in various sizes.

FIG. 84 is an overhead view of a first exemplary mass-customized tibialcomponent kinematic placement guide fabricated in accordance with theinstant disclosure.

FIG. 85 is a picture of a distal femur showing the location of variousmeasurements and landmarks.

FIG. 86 is a picture of a profile view of a femur showing the locationof various axes and landmarks.

FIG. 87 is a picture of a distal femur showing the location of variousaxes, landmarks, and planes.

FIG. 88 is a picture of a proximal femur showing the location of variousaxes, landmarks, and planes.

FIG. 89 is a picture of a profile view of a femur showing the naturallongitudinal curvature.

FIG. 90 is a picture of a proximal tibia showing the location of variousaxes, landmarks, and planes.

FIG. 91 is a picture of a profile view of a proximal tibia showing thelocation of various landmarks.

FIG. 92 is a picture of a profile tibia showing the mechanical axis ofthe tibia.

FIG. 93 is a picture of a distal tibia showing the location of the anklecenter.

FIGS. 94A-94D are pictures of various distal femurs showing the locationof the meniscal axis.

FIGS. 95A and 95B are images of the distal end of a femoral modelshowing how rotational changes with respect to the interface between thetibia and femur effect the shape of the trochlear groove.

FIG. 96 is a plot showing how quadriceps force changes as a function ofknee flexion.

FIG. 97 is a picture of a distal femur tangible model marked up to showthe medial boss as a blue line.

FIGS. 98A-98D are a series of views comparing the position of thefemoral component of a TKA using mechanical alignment and kinematicalignment and how the patella cannot track the femoral componentproperly using mechanical alignment.

FIGS. 99A and 99B are comparative frontal views of femoral componentsplaced via mechanical alignment (99A) and via kinematic alignment (99B).

FIGS. 100A and 100B are frontal and overhead views showing how currentfemoral components should be modified to account for correct kinematicalignment.

FIG. 101 is an image of a commercially available tibial tray properlyaligned via kinematic alignment, yet continuing to show posteriorcruciate ligament impingement, thus necessitating a revised designimplant to avoid impingement and be properly kinematically aligned whenmounted to the resected tibia.

FIG. 102 is a similar image to FIG. 101 showing posterior cruciateligament impingement using a present day implant when kinematicallyaligned, with the posterior cruciate ligament represented by its mostlikely locations from the statistical atlas.

FIGS. 103A-103C are a series of images highlighting the differences inshape between the current day femoral component (FIG. 103A) and afemoral component designed in accordance with the instant disclosure(FIG. 103B) and how the design shapes compare to one another near theend of the trochlear groove (FIG. 103C).

FIG. 104 is a graphical process flow diagram illustrating an exemplaryprocess sequence for creation of a mass customized kinematic alignmentguide or trial in accordance with the instant disclosure.

FIG. 105 is an overhead view of a first exemplary patient-specifickinematic alignment guide for use with a resected tibia.

FIGS. 106A and 106B are various views of a second exemplarypatient-specific kinematic alignment guide for use with a resected tibiashowing the placement of the guide with respect to the tibia and withrespect to the posterior cruciate ligament.

DETAILED DESCRIPTION

The exemplary embodiments of the present disclosure are described andillustrated below to encompass devices, methods, and techniques relatingto knee arthroplasty. Of course, it will be apparent to those ofordinary skill in the art that the embodiments discussed below areexemplary in nature and may be reconfigured without departing from thescope and spirit of the present disclosure. It is also to be understoodthat variations of the exemplary embodiments contemplated by one ofordinary skill in the art shall concurrently comprise part of theinstant disclosure. However, for clarity and precision, the exemplaryembodiments as discussed below may include optional steps, methods, andfeatures that one of ordinary skill should recognize as not being arequisite to fall within the scope of the present disclosure.

Referring to FIGS. 85-89, as used herein, the following are mechanicalneutral anatomic landmark definitions for the femur: (1)Transepicondylar Axis (TEA): The axis joining the most medial prominenceof the medial epicondyle and the most lateral prominence of the lateralepicondyle; (2) Posterior Condyle Axis (PCA): The axis joining the mostposterior points on the medial and lateral condyles of the distal femur;(3) Distal Anatomical Axis (DAA): The distal anatomical axis is definedby locating the shaft centroids at the distal one-third and distalone-fifth of the overall femur length; (4) Central AP Axis (CAP): Axisdefined with termini at the posterior aspect of the intercondylar notchand the most anterior portion of the intercondylar groove; (5) FemoralSaddle Point: A landmark located at the most distal extension of theintercondylar groove; (6) Knee Center: Using the two endpoints of theCAP measurement and the femoral saddle point, a plane is defined whichbisects the femur into medial and lateral sides. The intersection ofthis plane with the TEA is the knee center, which forms the distalendpoint of the mechanical axis (MA) of the femur; (7) Distal MechanicalEntry Point of the Femur: The distal entry of the medullary canal. Thislandmark is estimated to be at the intersection of the anatomical axisof the femur with its intercondylar notch; (8) Mechanical axis (MA):Axis defined by the femoral head center and knee center; (9) APDirection: Using the MA and the TEA, a mutually perpendicular vectorwith its origin at the knee center is used to define theantero-posterior (AP) direction, resulting in a direction similar toWhiteside's line; (10) Femoral AP Axis (FAA): Axis defined as thecross-product of the mechanical axis of the femur with the PCA; (11)Mediolateral Axis of the Femur (MLA): The cross-product of the femoralmechanical axis with its anteroposterior axis; (12) Femoral Head Center(FHC): Center of the sphere approximating femoral head; (13) AnteriorMedio-lateral Width (AML): The AP direction is used to locate the twomost anterior landmarks on the medial and lateral condyles of the distalfemur. Connecting the two most anterior points gives a measurement ofanterior medio-lateral width (AML) along the trochlear line; (14)Posterior Medio-lateral Width (PML): The AP direction is used to locatethe two most posterior points on the medial and lateral condyles of thedistal femur. Connecting the two most posterior points gives a measureof posterior medio-lateral width (PML) measured along the posteriorcondylar axis (PCA); (15) AP Length of Medial Condyle (MAP): Connectingthe pairs of medial vertices defined above, respectively, gives the APlength of the medial condyle; (16) AP Length of Lateral Condyle (LAP):Connecting the pairs of lateral vertices defined above, respectively,gives the AP length of the lateral condyle (LAP); (17) Overall APLength: The minimum distance between the prominences of the lateralanterior condyle and the posterior plane; (18) AP Angle: The angle ofthe AML vector relative to the posterior plane; (19) DistalMedial-lateral Length (DML): The most distal aspects of the medial andlateral condyles are recorded using MA as a reference direction. Thedistance between these two landmarks is denoted as DML; (20) PosteriorAngle (PA): The angle between the vector connecting the DML length andthe mean axis of the femur; (21) Condylar Twist Angle (CTA): The anglebetween the TEA and PCA; (22) Patellar Groove Height (GH): Calculatedbetween the posterior aspect of the intercondylar notch and the midpointbetween the two DML axis points; (23) Femoral Axis (FA): Line from thecenter of the femoral head to the center of the shaft at the level ofthe lesser trochanter. Anteversion (+) is ventral, retroversion (−) isdorsal; (24) Femoral Version: Angle comparing the femoral axis to thetransepicondylar axis; (25) Femoral Shaft Curvature (SC): The radius ofcurvature of the femoral mean axis; (26) Femoral implantflexion/extension: Rotation about the mediolateral axis of the femur.From a lateral perspective, clockwise rotation is called extension for aright femur and flexion for a left femur; (27) Femoral implantvarus/valgus angle: Rotation about the AP axis of the femur. From ananterior perspective in the frontal plane, clockwise rotation is calledvarus for a right femur and valgus for a left femur; (28) Femoralinternal/external rotation of the femoral implant: Rotation about themechanical axis of the femur. From a distal perspective in the axialplane, clockwise rotation is called internal rotation on a right femurand external rotation on a left femur. The system gives the operator theoption of expressing internal/external rotation relative to the TEA orthe PCA; (29) Femoral distal resection levels (medial and lateral): Thedistance between the distal cut plane and the most distal condylepoints, following the mechanical axis; (30) Femoral distal resectionlevel: A level on the side with the most distal condyle point; (31)Femoral posterior resection levels (medial and lateral): The distancesbetween the posterior cut plane and the most posterior points on themedial and lateral condyles.

Referencing FIGS. 90-93, as used herein, the following are mechanicalneutral anatomic landmark definitions for the tibia: (1) Mechanical axis(MA): the axis between the ankle joint center and the proximal entry ofthe medullary canal; (2) Proximal Entry of the Tibial Mechanical Axis:The proximal entry medullary canal. This landmark is estimated to be at33% anterior in the AP direction and at 50% of the transtibial axis,prolonged in medial and lateral to the bone surfaces; (3) IntercondylarEminence Points: The two highest projecting points on the medial andlateral intercondylar eminences; (4) Eminence Midpoint: The midpointbetween the lateral and medial intercondylar eminence points; (5) TibialTuberosity: The most anteriorly protruding point on the tibialtuberosity; (6) ML: Maximum width of the tibia plateau in themedial-lateral direction; (7) ML Axis of the Tibia: The cross-product ofits AP direction with its mechanical axis; (8) AP: Length of the tibialplateau in the anterior-posterior (AP) direction and passing through themidpoint of the tibial intercondylar eminence (i.e. eminence midpoint);(9) AP Direction: The axis that joins the center of the attachment areaof the posterior cruciate ligament (PCL) and a point on the medial thirdof the tibial tuberosity; (10) AP Axis of the Tibia: The cross-productof the tibia mechanical axis with its ML axis; (11) Eminence Width (EW):Distance between medial and lateral intercondylar eminence points; (12)Tibial Twist Angle (TTA): Angle between the AP direction and a lineconnecting the intercondylar eminence midpoint and tibial tuberosity;(13) Lateral Plateau Height (LPH): Length of the lateral tibial plateauin the AP direction; (14) Lateral Plateau Width (LPW): Length of thelateral tibial plateau in the ML direction; (15) Medial Plateau Height(MPH): Length of the medial tibial plateau in the AP direction; (16)Medial Plateau Width (MPW): Length of the medial tibial plateau in theML direction; (17) Eminence ML Ratio (EMLR): Ratio of MPW (i.e. medialplateau width) over ML; (18) Maximum Length: Length of the tibia fromthe medial malleolus to the intercondylar eminence; (19) PosteriorTibial Axis (PTA): Line connecting the most posterior surfaces of medialand lateral tibial plateau; (20) Transtibial Axis: Line connecting theanterior posterior midpoints of the medial and lateral tibial plateaus;(21) Tibial Center: Exact midpoint of the transtibial axis; (22) TibialTuberosity Angle (TTA): Angle formed by a line from the center point ofthe tibial tuberosity to the tibial center compared to the anteriortibial axis; (23) Ankle Center: Midpoint of the proximal talus articularsurface, about 45% lateral to the most medial prominence of thetransmalleolar axis; (24) Ankle Joint Center: The midpoint of the axisjoining the most lateral point of the lateral malleoli and the mostmedial point of the medial malleoli; (25) Transmalleolar Axis: Lineconnecting the prominence of the medial and lateral malleoli (or tips ofthe malleoli); (26) Slope of the Tibial Implant: Rotation about the MLaxis of the tibial. From a lateral side perspective, clockwise rotationis called anterior slope of extension for a right tibia and calledposterior slope or flexion for a left tibia; (27) Varus/valgus Angle ofthe Tibial Implant: Rotation about the AP axis of the tibia. From ananterior perspective in the frontal plane, clockwise rotation is calledvalgus for a right tibia and varus for a left tibia; (28)Internal/external Rotation of the Tibial Implant: Rotation about themechanical axis of the tibia. From a proximal perspective in the axialplane, clockwise rotation is called external rotation on a right tibiaand internal rotation on a left tibia. The system gives the user theoption of expression tibial rotation relative to the AP axis or the PTA;(29) Medial Resection Level of the Tibia: The distance between the cutplane and the most distal point on the medial plateau, following themechanical axis. Therefore, augmenting or diminishing the resectionlevel will translate the cut plane along the mechanical axis; (30)Lateral Resection Level of the Tibia: The distance between the cut planeand the most distal point on the lateral plateau, following themechanical axis. Therefore, augmenting or diminishing the resectionlevel will translate the cut plane along the mechanical axis.

Referring back to FIGS. 85-89, as used herein, the following arekinematic alignment definitions for the femur: (1) Projected PlaneNormal to PCA (PPNP): Intersection of plane normal to PCA with planenormal to tibia MA. The PPNP axis depends on the orientation of thefemur relative to the tibia; (2) Meniscal Axis: The axis extendingthrough the contact centers of the medial condyle and the lateralcondyle when in contact with the tibia in extension.

Referring back to FIGS. 90-93, as used herein, the following arekinematic alignment definitions for the tibia: (1) Posterior Tibial Axis(PTA): Line connecting the most posterior surfaces of the medial andlateral tibial plateau.

The instant disclosure relates to guides and trials for use with totalor partial knee replacement surgeries as well as femoral and tibialorthopedic implants. As will be discussed in more detail hereafter, theexemplary embodiments of the instant disclosure include tibial andfemoral placement guides to facilitate placement of the tibial andfemoral implant components, as well as methods of fabricating theseplacement guides, in addition to method of using the placement guides,as well as methods of fabricating and placing novel prostheticapparatuses that more closely approximate the natural kinematics of theknee in comparison to present day knee prosthetic components.

As discussed previously, present day placement of prosthetic kneecomponents is premised solely upon mechanical alignment. In particular,the center of the femoral head and center of the ankle (see FIG. 1),which are used by conventional, computer assisted surgery and personalcutting instruments to align TKA mechanically, have no bearing on thekinematics of the knee. And this mechanical alignment sacrificeskinematics as the mechanical references used for alignment areinconsistent with kinematic references, thereby leading to kinematicsthat are abnormal, patient discomfort, and premature joint failure.Instead, the present disclosure is premised upon taking a novel approachpremised upon kinematic alignment of prosthetic components.

Kinematic alignment of the knee is based on the normal kinematics of theknee. Kinematics in this context refers to the relative relationship ofthe femur, patella and tibia at any angle of flexion without loadbearing force applied to the knee. The knee joint surface, menisci, andligament structures determine the normal kinematic relationship amongthe femur, patella, and tibia. The following is a discussion ofpopulating a statistical atlas that will be described in more detailhereafter as part of generating mass-customized guides and orthopedicimplants in accordance with the instant disclosure.

A premise supporting kinematic alignment of the knee is accounting forand replicating three axes that govern the movement of the patella andtibia with respect to the femur. The primary axis of these three axes isa first transverse axis (i.e., helical axis) in the femur about whichthe tibia flexes and extends. In order to determine this firsttransverse axis of a knee joint, the instant disclosure makes use ofX-ray fluoroscopy to image the knee joint. More specifically, a kneejoint is imaged at distinct points throughout its range of motion (e.g.,between full extension and 160 degrees flexion). These fluoroscopicimages are registered to 3D models of the knee joint, as discussedpreviously, which are specific to that knee joint (i.e., patient andknee side specific). After registering the 3D model to the fluoroscopicimages, a first transverse axis fitting process is conducted.

The first transverse axis fitting process involves fitting a sphere orcylinder to each joint condyle and, using this shape fittinginformation, calculating the transverse axis. Specifically, a circularor cylindrical shape is fit to the articular surfaces of the femoral andtibial condyles ranging between 10 to 160 degrees of flexion (see FIGS.19-21). The hypothesis behind using the spherical or cylindrical axes isto approximate the true axis of rotation of the femur on the tibia. Inorder to determine the circular or cylindrical shape dimensions, for agiven three dimensional model replicating the morphology of the bones ofthe knee joint (tibia, fibula, femur), a point cloud is generated by acomputer software program from the 3D knee joint model, where each pointin the cloud represents a surface point on the articular surface inquestion (with two articular surfaces for the distal femur and twoarticular surfaces for the proximal tibia). Each point cloud is thenbest fit to either a sphere or cylinder with known dimensions, afterwhich the transverse axis extending through both spheres/cylinders iscalculated by the software program (see FIG. 22). The first transverseaxis is calculated across the range of motion captured by the 3D kneemodel, thus indicating how the transverse axis changes throughout therange of motion of the knee joint. In contrast to this kinematicalignment approach, conventional wisdom suggests that the TEA (clinicalor surgical) mechanical axis is the axis of rotation of the femur on thetibia (see FIGS. 26 and 27). But the TEA mechanical alignment results inlittle to no rotation between the femur and tibia (see FIG. 26), whichis by no means consistent with normal knee kinematics.

An ancillary axis to the first transverse axis for kinematic alignmentis the PCA. The PCA is approximately parallel to the transverse axis andmay be used in aligning the femur (see FIG. 31). After knowing the firsttransverse axis, the PCA is calculated by determining the most posteriorpoints on the medial and lateral condyles of the distal femur.

There is a second transverse axis, which is a second of the threekinematic axes, in the femur about which the patella flexes and extends(see FIGS. 32A-32D). This second transverse axis is parallel, proximal,and anterior to the first transverse axis in the femur about which thetibia flexes and extends. However, it is not easily reproduced orapproximated by a known biomechanical (or clinical) axis.

In order to determine the second transverse axis about which the patellaflexes or extends, the center of mass of the patella (Loci) is trackedwith respect to the femur using X-Ray fluoroscopy (see FIGS. 32A-33F).In particular, as discussed above, a knee joint is imaged at distinctpoints throughout its range of motion (e.g., between full extension and160 degrees flexion). These fluoroscopic images (including femur,patella, fibula, and tibia) are registered to 3D models of the kneejoint, as discussed previously, which are specific to that knee joint(i.e., patient and knee side specific). After registering the 3D modelto the fluoroscopic images, a second transverse axis fitting process isconducted.

This second transverse axis fitting process involves determining theposition of the patella loci (i.e., centroid) for each fluoroscopicimage. In exemplary form, a software package determines the loci foreach fluoroscopic image with respect to the femur. Each loci is thenplotted as a point with respect to the 3D femur model, which creates aseries of points—one for each fluoroscopy image—in 3D space with respectto the femur 3D model. The software then conducts a planar regression onthe loci points to establish a best fit plane, which is either parallelor almost parallel with the sagittal kinematic plane extending throughthe femur. Likewise, the fitting process involves fitting a sphere orcylinder to each patella loci and, using this shape fitting information,calculating the second transverse axis. Specifically, a circular orcylindrical shape is fit to the loci across a knee range of motion, forexample, between 10 to 160 degrees of flexion. It should be note thatthe loci points in 3D space essentially replicate a curve, and it isthis curve that is fit to the curvature of the sphere or cylinder. Thehypothesis behind using the spherical or cylindrical axes is toapproximate the true axis of rotation of the patella about the femur. Insum, the software best fits either a sphere or cylinder with knowndimensions to the loci points, after which the second transverse axisextending through the sphere/cylinder is calculated by the softwareprogram to be perpendicular to the sagittal kinematic plane. In contrastto this kinematic alignment approach, conventional orthopedic implantsthe patella groove angle is not parallel to or closely approximates aparallel orientation with respect to the sagittal plane. Moreover,quadriceps length is not restored by current implant designs (see FIGS.38-40).

The third of the three axes is a longitudinal axis in the tibia aboutwhich the tibia internally and externally rotates on the femur. Thislongitudinal axis is perpendicular to each of the first and secondtransverse axes in the femur. This longitudinal axis is parallel to thesagittal kinematic plane, which is perpendicular to the posterior PCA ofthe femur (see FIG. 41).

As part of the instant technique, the Projected Plane Normal to PCA(PPNP) (i.e., sagittal kinematic plane) was compared to traditionallandmarks (see FIGS. 42 and 43A, 43B). In addition, the sagittalkinematic plane was compared in both supine and weight bearing positionsfor the same subjects/patients (See FIGS. 44A, 44B and 45), with nosignificant differences being observed. What this means is that weightbearing images are not necessary as part of the instant process tocreate kinematic guides in accordance with the instant disclosure.

However, as part of the instant technique, a large angular rotation wasobserved between the PPNP and the ⅓ Tubercle-PCL of approximately 14degrees (see FIGS. 46-53B). Accordingly, the inventor concluded that adifferent tibial plate design for the kinematic alignment was needed.

Referring to FIG. 55, a flow diagram is illustrated for an exemplaryprocess in accordance with the instant disclosure. In particular, theflow diagram presents an exemplary process for determining the bestposition/pose for a given orthopedic implant. As will be discussed inmore detail hereafter, the output of the flow diagram is the positionthe orthopedic implant should occupy when mounted to bone or anotherorthopedic component. In order to utilize this best pose information,the instant disclosure makes use of novel alignment guides that includesreferences thereon to ensure proper alignment of the implantedorthopedic component.

The process flow diagram is carried out electronically as part of asoftware package that automatically calculates position of a givenorthopedic implant with respect to a template bone model or a patientspecific bone model. For purposes of explanation, it is presumed thatthe example refers to a patient specific case. Nevertheless, thoseskilled in the art will readily understand the applicability of theexemplary process flow in cases involving non-patient specific implantsand bone models (e.g., mass customized orthopedic implants and templatebone models).

As an initial matter, the patient's bone 3D bone model is virtually cutin accordance with protocols from the manufacturer of the orthopedicimplant in question. Using this virtual bone cut (VBC), an initialplacement of a virtual model of the intended orthopedic implant (VM) ispositioned in accordance with the anterior-posterior axis (see FIG.56A). This initial placement of the VM is transformed into a 2Dfootprint that overlaps the VBC, where the position of the footprint isevaluated (see FIG. 56B). In particular, this evaluation includesdetermining the axes of the 2D footprint and comparing these axes to theone or more of the transverse axes and the longitudinal axis discussedpreviously. Post evaluation, calculations are made of the 2D footprintof the VM with respect to the VBC to determine and to what extentoverhang and underhang areas are present. This evaluation makes use ofthe outline of the VBC and the 2D footprint of the VM (see FIGS. 57A and57B). In other words, if the 2D footprint of the VM leaves exposedportions of the VBC, these areas are referred to as underhang areas,whereas aspects of the 2D footprint of the VM extending beyond (i.e.,overhangs) the VBC are referred to as overhang areas. The calculationsconcerning overhang and underhang areas, in addition to calculationsshowing deviation between the axes of the 2D footprint of the VBC andone or more of the transverse axes and the longitudinal axis, aredirected to a threshold sequence to discern whether or not thedeviations are within a predetermined tolerance.

If the answer is “yes,” the pose information is visually made availablevia a user graphical interface to allow for human intervention andfurther error minimization. Presuming the human operator is satisfiedwith the pose (see FIG. 58B), the pose becomes final and an implantguide based upon this pose is fabricated. Conversely, if the humanoperator is unsatisfied with the pose (see FIG. 58A), a new pose isselected by the software (or manually by the operator) taking intoaccount certain transformation bounds. This newly selected pose step isalso the result if the threshold sequence determines that the deviationscalculated were not within acceptable tolerances. Presuming a new poseis selected/generated, the software generates a 2D footprint of theselected orthopedic implant in question for this revised pose, thenevaluates the revised pose, and calculates overhang and underhang areas.The calculations for the revised pose are evaluated by the thresholdsequence, where downstream subprocesses are repeated as necessary untilreaching the final pose for the orthopedic implant. At the time thefinal pose is confirmed, the software also generates instructionssufficient to select or fabricate the correct implant guide.

Referring to FIGS. 59-64, a series of commercially available tibialtrays are depicted via overhead views. In particular, in FIG. 59, thesefour commercially available tibial trays are identified as Existing #1,Existing #2, Existing #3, and Existing #4 and duplicated pictoriallyinto three separate rows. The first row, identified as AAP, correspondsto the current mechanical alignment techniques utilized to align thetibial tray with respect to the femur and femoral component as shown inFIGS. 60, 63, and 64. The current mechanical alignment technique for allfour existing tibial trays is depicted graphically in FIG. 60 withrespect to a resected tibia. As can be seen in FIG. 60, using mechanicalkeys for alignment results in the implants being rotated toward thelateral side (beyond 12 o'clock in the clockwise direction). Conversely,the second row, identified as PPNP, corresponds to the same fourcommercially available tibial trays, but this time having the tibialtrays implanted and aligned kinematically in accordance with the instantdisclosure as shown in FIGS. 61, 63, and 64. As can be seen in FIG. 61,proper kinematic alignment of present day tibial trays results in thetrays being rotated toward the medial side (beyond 12 o'clock in thecounterclockwise direction). What is also apparent in FIG. 61 is thatnone of these four commercially available tibial trays are designedstructurally to optimize kinematic alignment. Specifically, it can beseen that the current tibial trays, when kinematically aligned, resultin significant overlap for the lateral anterior portion and posteriormedial portion, whereas significant underlap is present in the posteriorlateral portion and the anterior medial portion. Finally, the third rowalso corresponds to a mechanical alignment technique that attempts havethe contour of the implant most closely approximate the contour of theresected tibia with an emphasis on anterior edge alignment, which isshown in FIGS. 62-64.

FIGS. 63 and 64 show individually the four exemplary current tibialtrays) being aligned on a resected tibia, two using prior art techniques(AAP, TechMah) and the third (PPNP) using the techniques disclosedherein for kinematic alignment. These figures simply supplement FIGS.60-62 that show the four current tibial trays superimposed onto the sameresected tibia for illustrative purposes and further confirm that noneof these four commercially available tibial trays is optimized forkinematic alignment given the overlap and underlap present whenkinematically aligned.

Turning to FIG. 65, an exemplary process flow diagram is depicted forcalculating the posterior condylar axis using a statistical atlas for atibia. As an initial starting point, in step (A), a generic bone modelof the tibia is propagated with the most posterior medial and lateralpoint on the surface of the tibia using the data from the statisticalatlas. Afterwards, in step (B), a planar regression is performed on thepropagated points to generate two planes, a first for the medial pointsand a second for the lateral points. Using each plane and the points, instep (C), a pair of axes are generated, one for the medial side and asecond for the lateral side, that are normal to a respective plane atthe center of the points. In step (D), a line is generated between themost posterior points on the medial and lateral side using the locationof the axes generated in step (C). Thereafter, in step (E), the crossproduct of the line in step (D) and the axes generated in step (C)generates a new axis corresponding to the true posterior direction.Using this true posterior direction, the statistical atlas is searchedfor only the two most posterior points in this true posterior direction,which are then used to generate the posterior condylar axis for thetibia. This same process is applicable to calculating the posteriorcondylar axis for the femur. FIG. 66 simply confirms that 2D imagingslices are less accurate for determining the posterior condylar axis forthe femur and tibia given that the axes are most often not parallel tothe plane the image slice is taken from. And FIG. 67 confirms that thefemoral posterior condylar axis reliably sets the rotation relative tothe tibia.

In view of the foregoing explanation, the following is an explanation ofthe process for generating a tibial, mass customized kinematic alignmentguide. As depicted in FIG. 104, In exemplary form, a statistical atlasis utilized to calculate and extract various data that will be utilizedas part of generating the mass customized kinematic alignment guide.This statistical atlas may be preexisting or may be newly generated. Forpurposes of explanation, construction of the statistical atlas follows.

The exemplary statistical atlas comprises a compilation of data frommultiple subjects that involves the knee joint. By way of example, thestatistical atlas may include various images and associated data derivedfrom human knees such as, without limitation, X-ray images, CT images,MRI images, or other imaging technology. In the case of MRI images, thestatistical atlas may include images of the soft tissue (e.g.,cartilage) of the knee joint. By way of further example, it is presumedthat the exemplary statistical atlas has been created from 100 MRIimages and 66 CT images. These 166 images were then segmented to create166 virtual joint models, which are also part of the statistical atlas.

Referring to FIGS. 69A-71C, the tibia from each virtual joint modelwithin the statistical atlas is subjected to a resection process. Aspart of this resection process, each tibia has a plane applied theretothat simulates the bone cut a surgeon would make during a total kneearthroplasty (TKA) procedure to remove the proximal end of the tibia,thereby leaving a planar tibial end. As those skilled in the art areaware, the tibial bone cut carried out during a TKA is preferably madeperpendicular to the sagittal plane. But absolute precision is notalways possible, leading to tibial bone cuts that may be angled ±5degrees from proximal to distal and ±5 degrees from medial to lateral,as well as having different heights ±1 millimeter from proximal todistal along the longitudinal length. Consequently, the resectionprocess is carried out upon each tibia model taking into account aperfect bone cut (±0 degrees from proximal to distal, and ±0 degreesfrom medial to lateral) in order to make a resection cut, within 1degree increments, for each combination between the ±15 degreedeviation.

Post resection, the contour (i.e., outline shape) of each resected tibiais determined to identify the outermost bounds. After the outermostbounds (i.e., outline shape) of the resected tibia have been determined,a number of calculations are undertaken with respect to these bounds tomeasure various aspect of the resected tibia. By way of example, and notlimitation, the following eight measurements were computed for eachresection: (1) M_ML, width of medial plateau; (2) M_AP, height of medialplateau; (3) L_ML, width of lateral plateau; (4) L_AP, height of lateralplateau; (5) BB_AP, overall anterior-posterior height; (6) BB_ML,overall medial-lateral width; (7) LLMLR, ratio of widths between thelateral and medial plateaus; and, (8) MLAPR, ratio of heights betweenthe lateral and medial plateaus. In other words, each resected tibiaincluded shape/outline data, as well as eight sets of measurement data.Referencing FIGS. 68A-68C, using this shape/outline data and themeasurement data, a clustering operation was undertaken to establishsize groupings across the population of the statistical atlas. For eachsize grouping, in this case six groupings, the average outline of theresected tibia was computed and utilized to form the shape outline of atibial kinematic guide.

Referring to FIGS. 72A-74C, it should be noted that this shape outlinemay be further refined by using data from the statistical atlas toaccount for ligament retention. By way of example, where the posteriorcruciate ligament is retained, the eventual orthopedic tibial implantshould not impinge or obstruct the ligament. In order to account for oneor more retained ligaments, the statistical atlas may include softtissue data reflecting the placement of one or more ligaments withrespect to the bones of the knee joint. By knowing the attachmentlocations on the bones of the knee joint where ligaments attach, theshape outline of the tibial kinematic guide can be altered to ensure theoutline does not overlap or otherwise impinge upon one or more locationswhere a ligament will be retained as part of a TKA. The most common ofthese alterations is a sweeping curved notch cut into the shape outlineto allow for retention of the posterior cruciate ligament.

In addition to utilizing the shape outline of the resected tibias fromthe statistical atlas, the statistical atlas is also utilized tocalculate the kinematic axes for each joint model. These kinematic axes,as discussed previously, are transformed into data that accompanies eachtibial bone model and the resulting bone model having been resected. Thekinematic axes data for each resected bone model within a given sizepopulation are averaged and superimposed onto the shape outline of theaverage tibia for each size group. In particular, the sagittal kinematicaxis of the femur from anterior to posterior is superimposed onto thetibial outline, in addition to the first transverse axis of the femur.Other axes may likewise be superimposed on to the average tibial shapeoutline for each size group. This superimposition is eventually utilizedto form structural signs informing the surgeon as to the position ofcertain kinematic axes with respect to the kinematic guide that, whenpositioned correctly to align its outline with that of the actualresected tibia during TKA, indicates the position of certain kinematicaxes with respect to the actual resected tibia.

Using the shape outline data and the superimposition data, a tibialguide may be constructed. A first exemplary mass customized kinematicguide for a tibial implant is shown in FIGS. 73A, 73B. This tibial guideis utilized by a surgeon to provide markings onto the resected tibiathat will guide the surgeon to correctly place the tibial orthopedicimplant. As can be seen, the guide includes a shape that closelyapproximates the outline of the resected tibia. In this fashion, thesurgeon would position the guide on top of the resected tibia to mostclosely match the contour/outline of the guide with the outline of theresected femur, which denotes the proper position of the guide. Theinterior area of the guide includes a single through opening. Thisthrough opening includes a pair of three-sided rectangular cutoutsextending in the posterior and anterior directions, that are near themiddle from medial to lateral, that are longitudinally aligned with oneanother on opposing edges of the cutouts. These cutouts correspond tothe femoral sagittal kinematic plane. It is envisioned that a surgeonwould use a hammer and corresponding rectangular drive bit, where thedrive bit was sized to fit within the bounds of the cutouts, to forcethe drive bit into the resected tibia and make a mark corresponding tothe femoral sagittal plane. Alternatively, the surgeon may use a markerto denote the locations of the cutouts. In either instance, the guidemay be thereafter removed to leave behind an indication of the locationof the femoral sagittal kinematic plane.

This first exemplary mass customized kinematic guide also includes acontour on the posterior side to account for retention of the posteriorcruciate ligament (PCL). In addition, the posterior portion of the guideincludes a series of projections that lie on opposing sides of the PCLcontour. These projections represent the location of the tibial PCA,which should be aligned with the most posterior points of the medial andlateral condyles. The surgeon may utilize these projections to ensurethe guide is properly positioned with respect to the tibia.

As shown in FIGS. 74A-74C, a first alternate exemplary mass customizedkinematic guide for a tibial implant is identical to the first exemplarymass customized kinematic guide for a tibial implant, with the exceptionof the posterior projections. Instead of projections, the firstalternate exemplary mass customized kinematic guide for a tibial implantincludes a pair of rectangular recesses on opposing sides of the PCLcontour. These recesses are sized to accept a corresponding style thatextends posteriorly and distally from the guide. When inserted in to acorresponding recess, the styles cooperate to establish a posterior stopagainst which posterior portion of the resected tibia contacts toinhibit further anterior repositioning of the guide during the initialguide placement. In exemplary form, when the styles are inserted in to acorresponding recess, the surgeon uses the styles along with the outlineshape of the guide to correctly position the guide with respect to theresected femur. Once correctly positioned, the surgeon may utilize theguide to make marks or attach fasteners to the top of the resected tibiato provide an indication of the placement of one or more axes of thefemur.

Referring to FIG. 84, again using the shape outline data and thesuperimposition data, a tibial guide may be constructed. This secondexemplary mass customized kinematic guide for a tibial implant is alsointended to be utilized by a surgeon to provide markings (and/or attachpins or other fasteners) onto the resected tibia that will guide thesurgeon to correctly place the tibial orthopedic implant. As can beseen, the guide includes a shape that closely approximates the outlineof the resected tibia. In this fashion, the surgeon would position theguide on top of the resected tibia to most closely match thecontour/outline of the guide with the outline of the resected femur,which denotes the proper position of the guide. The interior area of theguide includes T-shaped through opening along with four circularopenings, two on opposing sides of the T-shaped opening. This T-shapedthrough opening includes an elongated media to lateral section (top,horizontal portion of the T), as well as an elongated posterior toanterior section (vertical portion of the T). The elongated medial tolateral section of the T-shaped opening corresponds to an axis inparallel with the femur PCA, while the elongated posterior to anteriorsection of the T-shaped opening corresponds to the femoral sagittalkinematic plane. The four circular openings are sized to receive pins orother fasteners that are mounted to the resected tibia and retainedafter the tibial guide is removed from the resected tibia.

In addition to the openings formed through this second exemplary masscustomized kinematic guide, the guide also includes various indicia. Inparticular, the face of the guide opposite the resected tibia includes a“MED” indicia indicating to a surgeon that this side of the guide shouldbe aligned with the medial portion of the tibia. In order for thesurgeon to quickly know whether the guide is for the right tibia or theleft tibia, the face includes a “R” indicia indicating that this guideis for use with the right tibia. In cases where the guide is fabricatedto correspond to the left tibia, this “R” would be replaced with an “L.”Finally, the face of the guide also includes a size indicia, in thiscase a “4” indicating to the surgeon that this guide is a size four.Should the initial selection of the guide be too large or small, thesurgeon can quickly request a smaller or larger size guide and operatingroom assistants can quickly discern the size of the guide using thissize reference indicia. And similar to the first exemplary masscustomized kinematic guide, this second exemplary mass customizedkinematic guide also includes a contour on the posterior side to accountfor retention of the posterior cruciate ligament (PCL).

Referring to FIGS. 77, 78A, 78B, and 83, again using the shape outlinedata and the superimposition data, a further tibial guide may beconstructed. This third exemplary mass customized kinematic guide for atibial implant is also intended to be utilized by a surgeon to providemarkings (and/or attach pins or other fasteners) onto the resected tibiathat will guide the surgeon to correctly place the tibial orthopedicimplant. As can be seen, the guide includes a shape that closelyapproximates the outline of the resected tibia. In this fashion, thesurgeon would position the guide on top of the resected tibia to mostclosely match the contour/outline of the guide with the outline of theresected femur, which denotes the proper position of the guide. Theinterior area of the guide includes single through opening along withalong with a pair of cutouts. The single through opening includes anenlarged anterior opening to accommodate tibial broach throughput.Extending off of this enlarged opening is a first pair of cutoutsextending in the medial and lateral directions, terminating in circularopenings. The circular openings are sized and configured to receive pinsor other fasteners that are mounted to the resected tibia and retainedafter the guide is removed from the resected tibia. The dominant lengthof these first cutouts are delineated by parallel walls that cooperateto establish an axis that is parallel with the femoral PCA. A second setof cutouts extends in the posterior and anterior directions. Thesecutouts are representative of the location of the femoral sagittalkinematic plane. Finally, extending posteriorly and in the medial andlateral directions are a third set of cutouts that provide an area forlarger fasteners or larger markings to be made onto the resected tibia.

Similar to the first and second exemplary mass customized kinematicguides, this third exemplary mass customized kinematic guide alsoincludes a contour on the posterior side to account for retention of theposterior cruciate ligament (PCL). A fourth set of cutouts is formed onopposing sides of this posterior contour. These fourth cutouts extend inthe medial and lateral directions, terminating in circular openings. Thecircular openings are sized and configured to receive pins or otherfasteners that are mounted to the resected tibia and retained after theguide is removed from the resected tibia. The dominant length of thesefourth cutouts are delineated by parallel walls that cooperate toestablish an axis that is parallel with the femoral PCA.

In addition to the openings formed through this third exemplary masscustomized kinematic guide, the guide also includes various indicia. Inparticular, the face of the guide opposite the resected tibia includes a“MED” indicia indicating to a surgeon that this side of the guide shouldbe aligned with the medial portion of the tibia. In order for thesurgeon to quickly know whether the guide is for the right tibia or theleft tibia, the face includes a “R” indicia indicating that this guideis for use with the right tibia. In cases where the guide is fabricatedto correspond to the left tibia, this “R” would be replaced with an “L.”Finally, the face of the guide also includes a size indicia, in thiscase a “4” indicating to the surgeon that this guide is a size four.Should the initial selection of the guide be too large or small, thesurgeon can quickly request a smaller or larger size guide and operatingroom assistants can quickly discern the size of the guide using thissize reference indicia.

While the foregoing explanation has been directed to processes andgeneration of mass customized tibial kinematic guides, it should benoted that patient-specific guides can be fabricated in accordance withthe instant disclosure. Consequently, the following is an exemplaryexplanation of the process and resulting fabrication of a patientspecific tibial kinematic guide.

Referring to FIG. 75, the following is an explanation of the process forgenerating a tibial, patient-specific kinematic alignment guide. Inexemplary form, images of the patient knee joint are taken from one ormore imaging modalities including, without limitation, X-ray images, CTimages, ultrasound, and MRI images. In the case of MRI images, thepatient knee joint images may include images of the soft tissue (e.g.,cartilage) of the knee joint. These patient images are then segmented tocreate a patient-specific virtual joint model using a software program.Those skilled in the art are familiar with segmentation and utilizing 2Dimages to form a virtual 3D model.

The tibia from the patient-specific virtual joint model is subjected toa resection process using a software resection algorithm. As part ofthis resection process, the tibia has a plane applied thereto thatsimulates the bone cut a surgeon would make during a total kneearthroplasty (TKA) procedure to remove the proximal end of the tibia,thereby leaving a planar tibial end. As those skilled in the art areaware, the tibial bone cut carried out during a TKA is preferably madeperpendicular to the sagittal plane. But absolute precision is notalways possible, leading to tibial bone cuts that may be angled ±5degrees from proximal to distal and ±5 degrees from medial to lateral,as well as having different heights ±1 millimeter from proximal todistal along the longitudinal length. Consequently, the resectionprocess is carried out upon the tibia model taking into account aperfect bone cut (±0 degrees from proximal to distal, and ±0 degreesfrom medial to lateral) in order to make a resection cut, within 1degree increments, for each combination between the ±5 degree deviation.

Post resection, the contour (i.e., outline shape) of the resected tibiais determined to identify the outermost bounds using a software contouralgorithm. After the outermost bounds (i.e., outline shape) of theresected tibia have been determined, a number of calculations areundertaken with respect to these bounds to measure various aspect of theresected tibia. By way of example, and not limitation, the followingeight measurements were computed for each resection: (1) M_ML, width ofmedial plateau; (2) M_AP, height of medial plateau; (3) L_ML, width oflateral plateau; (4) L_AP, height of lateral plateau; (5) BB_AP, overallanterior-posterior height; (6) BB_ML, overall medial-lateral width; (7)LLMLR, ratio of widths between the lateral and medial plateaus; and, (8)MLAPR, ratio of heights between the lateral and medial plateaus. Inother words, each resected tibia includes shape/outline data, as well aseight sets of measurement data. Using this shape/outline data and themeasurement data, the size and outline of the resected tibia is computedand utilized to form the shape outline of the patient-specific tibialkinematic guide.

It should be noted that this shape outline may be further refined byusing data from the patient-specific images to account for ligamentretention. By way of example, where the posterior cruciate ligament isretained, the orthopedic tibial implant should not impinge or obstructthe ligament. In order to account for one or more retained ligaments,the patient-specific virtual model of the knee joint includes one ormore ligaments with respect to the bones of the knee joint. By knowingthe attachment locations on the bones of the knee joint where ligamentsattach, the shape outline of the patient-specific tibial kinematic guidecan be altered to ensure the outline does not overlap or otherwiseimpinge upon one or more locations where a ligament will be retained aspart of a TKA. The most common of these alterations is a sweeping curvednotch cut into the shape outline to allow for retention of the posteriorcruciate ligament.

In addition to generating the shape and size of the patient-specifickinematic guide, the computer program also calculates the kinematic axesfor the patient-specific joint model using one or more axis/axesalgorithms. These calculated kinematic axes, as discussed previously,are transformed into data that accompanies the tibial bone model and theresulting tibial bone model post resection. The kinematic axes data forthe resected tibial bone model is superimposed onto the shape outline ofthe bone model. In particular, the sagittal kinematic axis of the femurfrom anterior to posterior is superimposed onto the shape outline, inaddition to the first transverse axis of the femur. Other axes maylikewise be superimposed onto the tibial shape outline for. Thissuperimposition is eventually utilized to form structural signsinforming the surgeon as to the position of certain kinematic axes withrespect to the kinematic guide that, when positioned correctly to alignits outline with that of the actual resected tibia during TKA, indicatesthe position of certain kinematic axes with respect to the actualresected tibia.

Using the shape outline data and the superimposition data, apatient-specific tibial guide may be constructed. A first exemplarypatient-specific kinematic guide for a tibial implant is shown in FIGS.105, 106A, and 106B. This tibial guide is utilized by a surgeon toprovide markings onto the resected tibia that will guide the surgeon tocorrectly place the tibial orthopedic implant. As can be seen, the guideincludes a shape that precisely mirrors the outline of the resectedtibia. In this fashion, the surgeon would position the guide on top ofthe resected tibia to most closely match the contour/outline of theguide with the outline of the resected femur, which denotes the properposition of the guide. The interior area of the guide includes a singlethrough opening. This through opening includes a pair of three-sidedrectangular cutouts extending in the posterior and anterior directions,that are near the middle from medial to lateral, that are longitudinallyaligned with one another on opposing edges of the cutouts. These cutoutscorrespond to the femoral sagittal kinematic plane. It is envisionedthat a surgeon would use a hammer and corresponding rectangular drivebit, where the drive bit was sized to fit within the bounds of thecutouts, to force the drive bit into the resected tibia and make a markcorresponding to the femoral sagittal plane. Alternatively, the surgeonmay use a marker to denote the locations of the cutouts. In eitherinstance, the guide may be thereafter removed to leave behind anindication of the location of the femoral sagittal kinematic plane.

This first exemplary patient-specific kinematic guide also includes acontour on the posterior side to account for retention of the posteriorcruciate ligament (PCL). In addition, the posterior portion of the guideincludes a series of projections that lie on opposing sides of the PCLcontour. These projections represent the location of the tibial PCA,which should be aligned with the most posterior points of the medial andlateral condyles. The surgeon may utilize these projections to ensurethe guide is properly positioned with respect to the tibia.

As shown in FIG. 74, a first alternate exemplary patient-specifickinematic guide for a tibial implant is identical to the first exemplarypatient-specific kinematic guide for a tibial implant, with theexception of the posterior projections. Instead of projections, thefirst alternate exemplary patient-specific kinematic guide for a tibialimplant includes a pair of rectangular recesses on opposing sides of thePCL contour. These recesses are sized to accept a corresponding stylethat extends posteriorly and distally from the guide. When inserted into a corresponding recess, the styles cooperate to establish a posteriorstop against which posterior portion of the resected tibia contacts toinhibit further anterior repositioning of the guide during the initialguide placement. In exemplary form, when the styles are inserted in to acorresponding recess, the surgeon uses the styles along with the outlineshape of the guide to correctly position the guide with respect to theresected femur. Once correctly positioned, the surgeon may utilize theguide to make marks or attach fasteners to the top of the resected tibiato provide an indication of the placement of one or more axes of thefemur.

Referring to FIG. 84, again using the shape outline data and thesuperimposition data, a tibial guide may be constructed. This secondexemplary patient-specific kinematic guide for a tibial implant is alsointended to be utilized by a surgeon to provide markings (and/or attachpins or other fasteners) onto the resected tibia that will guide thesurgeon to correctly place the tibial orthopedic implant. As can beseen, the guide includes a shape that mirrors the outline of theresected tibia. In this fashion, the surgeon would position the guide ontop of the resected tibia to most closely match the contour/outline ofthe guide with the outline of the resected femur, which denotes theproper position of the guide. The interior area of the guide includesT-shaped through opening along with four circular openings, two onopposing sides of the T-shaped opening. This T-shaped through openingincludes an elongated media to lateral section (top, horizontal portionof the T), as well as an elongated posterior to anterior section(vertical portion of the T). The elongated medial to lateral section ofthe T-shaped opening corresponds to an axis in parallel with the femurPCA, while the elongated posterior to anterior section of the T-shapedopening corresponds to the femoral sagittal kinematic plane. The fourcircular openings are sized to receive pins or other fasteners that aremounted to the resected tibia and retained after the tibial guide isremoved from the resected tibia.

In addition to the openings formed through this second exemplarypatient-specific kinematic guide, the guide also includes variousindicia. In particular, the face of the guide opposite the resectedtibia includes a “MED” indicia indicating to a surgeon that this side ofthe guide should be aligned with the medial portion of the tibia. Inorder for the surgeon to quickly know whether the guide is for the righttibia or the left tibia, the face includes a “R” indicia indicating thatthis guide is for use with the right tibia. In cases where the guide isfabricated to correspond to the left tibia, this “R” would be replacedwith an “L.” Finally, the face of the guide also includes a sizeindicia, in this case a “4” indicating to the surgeon that this guide isa size four. Should the initial selection of the guide be too large orsmall, the surgeon can quickly request a smaller or larger size guideand operating room assistants can quickly discern the size of the guideusing this size reference indicia. And similar to the first exemplarypatient-specific kinematic guide, this second exemplary patient-specifickinematic guide also includes a contour on the posterior side to accountfor retention of the posterior cruciate ligament (PCL).

Referring to FIGS. 77, 78A, 78B, and 83, again using the shape outlinedata and the superimposition data, a further tibial guide may beconstructed. This third exemplary patient-specific kinematic guide for atibial implant is also intended to be utilized by a surgeon to providemarkings (and/or attach pins or other fasteners) onto the resected tibiathat will guide the surgeon to correctly place the tibial orthopedicimplant. As can be seen, the guide includes a shape that closelyapproximates the outline of the resected tibia. In this fashion, thesurgeon would position the guide on top of the resected tibia to mostclosely match the contour/outline of the guide with the outline of theresected femur, which denotes the proper position of the guide. Theinterior area of the guide includes single through opening along withalong with a pair of cutouts. The single through opening includes anenlarged anterior opening to accommodate tibial broach throughput.Extending off of this enlarged opening is a first pair of cutoutsextending in the medial and lateral directions, terminating in circularopenings. The circular openings are sized and configured to receive pinsor other fasteners that are mounted to the resected tibia and retainedafter the guide is removed from the resected tibia. The dominant lengthof these first cutouts are delineated by parallel walls that cooperateto establish an axis that is parallel with the femoral PCA. A second setof cutouts extends in the posterior and anterior directions. Thesecutouts are representative of the location of the femoral sagittalkinematic plane. Finally, extending posteriorly and in the medial andlateral directions are a third set of cutouts that provide an area forlarger fasteners or larger markings to be made onto the resected tibia.

Similar to the first and second exemplary patient-specific kinematicguides, this third exemplary patient-specific kinematic guide alsoincludes a contour on the posterior side to account for retention of theposterior cruciate ligament (PCL). A fourth set of cutouts is formed onopposing sides of this posterior contour. These fourth cutouts extend inthe medial and lateral directions, terminating in circular openings. Thecircular openings are sized and configured to receive pins or otherfasteners that are mounted to the resected tibia and retained after theguide is removed from the resected tibia. The dominant length of thesefourth cutouts are delineated by parallel walls that cooperate toestablish an axis that is parallel with the femoral PCA.

In addition to the openings formed through this third exemplarypatient-specific kinematic guide, the guide also includes variousindicia. In particular, the face of the guide opposite the resectedtibia includes a “MED” indicia indicating to a surgeon that this side ofthe guide should be aligned with the medial portion of the tibia. Inorder for the surgeon to quickly know whether the guide is for the righttibia or the left tibia, the face includes a “R” indicia indicating thatthis guide is for use with the right tibia. In cases where the guide isfabricated to correspond to the left tibia, this “R” would be replacedwith an “L.” Finally, the face of the guide also includes a patientindicia, in this case a last name or abbreviated name indicating to thesurgeon that this guide is for a particular patient in order todistinguish one patient-specific guide from another patient-specificguide.

In addition to tibial guides, the present disclosure also provides fortibial orthopedic trials that are mass customized and patient-specific.FIGS. 73 and 74 show exemplary tibial orthopedic trials. It should beunderstood that the foregoing guides may be modified to include a flangearound the periphery of the footprint that would operate to transformthe guide into a tibial tray trial. In this fashion, the trial would beshaped to accept a tibial tray trial insert in order to test fit thesize and location of the trial orthopedic before the final orthopedicimplants are permanently implanted. It should further be noted that theperipheral flange is only one modification that may be make todifferentiate a guide from a trial. In certain circumstances, the guidesdisclosed herein may be utilized as trials without having any structuralchanges in that the tibial tray inserts are configured to engage theguides for test fitting, thereby allowing the guides to function astrials too.

An exemplary sequence will now be described for use of the exemplarytibial guides and trials. In particular, those skilled in the art arefamiliar with total knee arthroplasty. Accordingly, a detaileddiscussion of all procedures performed is unnecessary and certainprocedures have been omitted in furtherance of brevity. In order toprepare the tibia for implantation of an orthopedic component, thesurgeon resects the tibia to remove the proximal end of the tibia toleave a relatively planar surface to which the eventual tibial trayimplant will sit. After the tibia has been resected, the surgeon obtainsa medial or lateral guide and places the guide on the resected surface.In the case of a mass-customized guide, the surgeon will choose a guidesize and orient the guide so that the outer periphery of the guide bestmatches or aligns with the outline of the resected tibia. While thispositioning is not as precise as a patient specific approach, itnonetheless provides greater accuracy to replicate natural kinematicsthat using mechanical alignment techniques. In the context of apatient-specific guide, the surgeon will orient the guide to preciselyoverlay and align the guide so that the outer contours of the guidematch or align themselves with the same contours of the resected tibia.

In either instance, after positioning the guide on top of the resectedtibia and aligning the guide, the surgeon can than make a mark, indicia,or other visual representation onto the surface of the resected tibia byusing one of the openings of the guide. By way of example, one of thethrough openings in the guide may be oriented in parallel to the femoralpost condylar axis. If the surgeon wishes to align the tibial traycomponent with respect to this reference axis, the surgeon may use apunch and drive it through the opening in the guide in order to make anindentation into the surface of the resected femur. In addition oralternatively, the surgeon may use a biologically acceptable marker anddraw the reference axis onto the resected tibia using the guide toorient the mark.

As discussed previously, the guides in accordance with the instantdisclosure may provide openings that allow for one or more referenceaxes or planes to be carried over to the resected tibia from the femur.The surgeon, depending upon his preference, may use one or more of theseopenings to make marks or other visually perceptible notations upon theresected tibia that will remain as one or more points of reference.After making one or more marks, the guide may be removed from the tibia.

In an instance where the guide doubles as a trial tibial tray, postmarkings, the surgeon may retain the guide/trial on top of the resectedtibia and mount to it one or more tibial tray insert trials that allowthe surgeon to test the size and orientation of the ultimate tibial trayand tray insert. When using the guide that doubles as a trial, thesurgeon may nonetheless make any markings desired onto the resectedtibia and thereafter remove the tibia guide/trial to carry out furtherprocedures to prepare the resected tibia to receive the final tibialtray implant. But it should be note that, for example, it is within thescope of the disclosure for the guide/trial to include a large enoughopening to accommodate through put of a broach or other reaminginstrument while retaining the guide/trial in position on top of theresected tibia.

In addition to tibial guides, the present disclosure also provides fortibial tray orthopedic implants that are mass customized andpatient-specific. The orthopedic components may be fabricated preciselyas discussed above with respect to the guides and trials in terms of theshape of the tibial tray and, in addition, include a tibial stem adapteron the underside of the plate that receives a tibial tray stem.Accordingly, a detailed description that is redundant process ofcreating one or more bone models, calculating relevant landmarks for thebones of the model, performing a virtual tibia resection along withaccounting for expected cut deviations, creation of plate contours thataccount for soft tissue and thereafter aligning various axes and planeswith respect to the resected tibia, and in the case of a mass customizeimplant, extracting the contour features and clustering the contourfeatures to establish one or more shapes and sizes that account for softtissue retention (e.g., the posterior cruciate ligament), with respectto the creation of tibial tray plates has been omitted in furtherance ofbrevity. Nevertheless, to the extent necessary for basis in claiming amass customized or patient-specific tibial tray orthopedic implant, theprior disclosure directed to fabricating guides and trials isincorporated herein by reference.

While the foregoing disclosure has been directed to the tibial side of aknee arthroplasty procedure, many of the foregoing processes andtechniques are applicable to the femur and alignment of the femoralorthopedic implant component. By way of introduction, when the knee isin significant flexion, a large component of quadriceps force compressesthe patella against the femur (see FIG. 96). The resultant joint stressis dictated by the size of the patellofemoral contact area, andpatellofemoral cartilage congruity determines that surface area.Conversely, when the knee is at or near full extension, the quadricepsgenerates predominantly tibiofemoral compression in addition to theground reaction generated by both the head, arm and trunk (HAT) and thelimb in swing phase. Therefore, joint stress in the extended knee isdictated primarily by tibiofemoral cartilage congruity. Moreover, thiscurve explains why patients with patellofemoral joint derangements areable to perform physical exercise against resistance with less pain ifthe knee flexion is kept lower than 20 degrees.

The adult human knee is thus a complex interaction product of itshabitual motion pattern as produced by the interactions of condylar formand ligamentous restraint, dictated by positional information, andcartilage/fibrous tissue modeling throughout ontogeny. As a consequence,when both processes ceased development at adulthood, the myriad fiberlengths within its restraint systems have remained congruent with thejoint's condylar surface geometry, and in the adult will continue towork together, maintaining a normal stereotyped motion pattern such thatthe velocity vectors of the two rigid bodies are uniformly tangent totheir points of contact throughout the joint's normal range of motion(See FIG. 104).

Such modeling provides an explanation for a unique feature of the humanknee, its medial condylar boss (see FIG. 97). This structure isobviously present in both dissections and dry specimens and trulyreflects its contact throughout development, to the medial meniscus. Itis never seen in the distal femur of other primates or mammals, and is adistinct, spiral, surface swelling of the medial condylar surfaceimmediately distal to its meniscal groove (i.e., the “medial obliquegroove” of the femur).

As mentioned previously, the combination of cartilage modeling and thehabitual contact of the distal femoral surface with the anterior portionof the medial and lateral menisci leaves small corresponding grooves onthe dry femur, the medial and lateral meniscal grooves. A lineconnecting these grooves, the meniscal axis (see FIG. 97, blue line),thus defines the position of the tibial plateau during full extension ofthe joint. This axis can be used to functionally orient the femur forfurther anatomical observation (see FIGS. 94A-94D).

As seen in FIGS. 95A, 95B, 98A-98D, 99A, and 99B, kinematically alignedcomponents will have different patellofemoral forces than mechanicalalignment in both extension and flexion. From published clinical resultsand visible in FIGS. 98A-98D, during flexion the location of trochleargroove is close to the normal anatomy in kinematically alignedknees—indicating potentially improved patellofemoral function duringflexion. In extension, however, current implants lateralize the patellain mechanically neutral alignment, reducing patellofemoral forces inextension. When existing components are placed in kinematic alignment,there are increased patellofemoral forces in extension.

Previous systems must strike a balance between performance in flexionand performance in extension.

Using the meniscal axis in FIG. 97, the femoral surface can befunctionally divided into flexion (red in FIG. 97) and extensionsurfaces (orange in FIG. 97). The extension surface for use in kinematicalignment can be optimized in a way that reduces risk of subluxation inmultiple ways. First, if it is desirable to keep the natural trochleargroove Q angle, the lateral aspect of the anterior flange must be raisedto resist the increased patellofemoral forces (relative to currentdesigns). This raised aspect is seen in FIG. 103C. An alternative is towiden, or lateralize the patellar groove in extension, reducing Q angleand thus reducing patellofemoral forces. A suggested widening of thegroove and increase in lateral surface area are seen in FIGS. 100A,100B. FIGS. 99A and 99B show reduction in lateral anterior surface areafor a kinematically aligned femoral component (left) versus themechanically aligned femoral component (right).

The tibial footprint of existing systems also can benefit fromoptimization for kinematic alignment. FIGS. 101 and 102 provide overlaysof existing system and kinematic alignment plate design, highlightingpotential issues with current designs that often require undersizing ofthe component due to anterior overhang or impingement with the posteriorcruciate ligament. Using process outlined in FIG. 104, the footprint ofthe tibial implant can be matched to the anatomy when in kinematicalignment.

Following from the above description and invention summaries, it shouldbe apparent to those of ordinary skill in the art that, while themethods and apparatuses herein described constitute exemplaryembodiments of the present invention, it is to be understood that theinventions contained herein are not limited to the above preciseembodiment and that changes may be made without departing from the scopeof the invention as defined by the following proposed points of novelty.Likewise, it is to be understood that it is not necessary to meet any orall of the identified advantages or objects of the invention disclosedherein in order to fall within the scope of the invention, sinceinherent and/or unforeseen advantages of the present invention may existeven though they may not have been explicitly discussed herein.

What is claimed is: 1-19. (canceled)
 20. A method of using a tibialcomponent placement guide for use in a knee arthroplasty procedureinvolving a knee joint comprising a tibia, a patella, and a femur, themethod comprising: applying an overlay to a resected tibia, the overlayincluding at least one of an indicia and an opening indicative of atleast one of an orientation and a position of at least one of a firstaxis of the femur, a second axis of the femur, and a first axis of thepatella; marking the resected tibia with at least one mark using theoverlay to denote at least one of an orientation and a position of atleast one of a first axis of the femur, a second axis of the femur, anda first axis of the patella; and, orienting and attaching at least oneof an orthopedic tibial tray trial and an orthopedic tibial tray to theresected tibia using the mark.
 21. The method of claim 20, wherein thestep of applying the overlay includes aligning a peripheral shape of theoverlay with a peripheral shape of the resected tibia and placing theoverlay on top of the resected tibia.
 22. The method of claim 20,wherein the overlay includes an opening indicative of the orientation ofthe first axis of the femur and the second axis of the femur.
 23. Themethod of claim 22, wherein the opening comprises a through hole. 24.The method of claim 23, wherein: the through hole outlines a T-shape; ahorizontal aspect of the T-shape is indicative of orientation of thefirst axis of the femur; and, a vertical aspect of the T-shape isindicative of orientation of the second axis of the femur.
 25. Themethod of claim 23, wherein: the through hole outlines a + shape; ahorizontal aspect of the + shape is indicative of orientation of thefirst axis of the femur; and, a vertical aspect of the + shape isindicative of orientation of the second axis of the femur.
 26. Themethod of claim 22, wherein: the opening comprises a first through holeand a second through hole; the first through hole is indicative of thefirst axis of the femur; and, the second through hole is indicative oforientation of the second axis of the femur.
 27. The method of claim 22,wherein: the opening comprises a first cutout and a second cutout; thefirst cutout is indicative of the first axis of the femur; and, thesecond cutout is indicative of orientation of the second axis of thefemur.
 28. The method of claim 20, wherein the first axis of the femurcomprises the posterior condylar axis of the femur.
 29. The method ofclaim 20, wherein the second axis of the femur comprises the helicalaxis of the femur.
 30. The method of claim 20, wherein the overlay has acontour outline that is aligned with the resected tibia.
 31. The methodof claim 30, wherein the contour outline is patient-specific.
 32. Themethod of claim 20, further comprising at least one of an indicia and anopening indicative of at least two of a medial guide, a lateral guide, asize of the guide, and a particular patient.
 33. The method of claim 20,wherein the guide is fabricated from at least one of titanium, atitanium alloy, stainless steel, and a stainless steel alloy.
 34. Themethod of claim 20, wherein the guide includes a through apertureconfigured to align a through fastener mounted to the resected tibia.35. The method of claim 34, wherein the through fastener comprises apin.
 36. The method of claim 35, wherein: the through aperture comprisesa plurality of through apertures; each of the plurality of apertures isconfigured to receive a pin.
 37. The method of claim 20, wherein theoverlay comprises a base plate.
 38. The method of claim 37, wherein thebase plate includes a flange along a periphery of the base plate. 39.The method of claim 20, wherein the overlay further comprises at leastone of an indicia and an opening indicative of the orientation of athird axis of the femur, the third axis being parallel to the firstaxis.
 40. The method of claim 20, wherein: the at least one markcomprises a pin; and, the step of marking the resected tibia includesfastening the at least one pin to the resected tibia.
 41. The method ofclaim 20, wherein: the at least one mark comprises an indentation formedinto the resected tibia; and, the step of marking the resected tibiaincludes using a punch to form the indentation into the resected tibia.42. The method of claim 20, wherein: the at least one mark comprises arepresentation formed into the resected tibia; and, the step of markingthe resected tibia includes writing the representation onto the resectedtibia.
 43. The method of claim 20, wherein the orienting and attachingstep includes orienting and attaching an orthopedic tibial tray to theresected tibia using the mark.
 44. The method of claim 20, furthercomprising removing the overlay prior to orienting and attaching atleast one of the orthopedic tibial tray trial and the orthopedic tibialtray to the resected tibia using the mark. 45-49. (canceled)
 50. Amethod of fabricating a tibial component placement guide for use in aknee arthroplasty procedure involving a knee joint comprising a tibia, apatella, and a femur, the method comprising: generating a tibialcomponent placement guide that typifies at least one of a shape and anoutline of a resected tibia, along with at least one identifierrepresentative of at least one of a position and an orientation of akinematic axis of at least one of the femur and the patella. 51-104.(canceled)